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L_0136 | earthquake safe structures | T_1089 | Why arent all structures in earthquakes zones constructed for maximum safety? Cost, of course. More sturdy structures are much more expensive to build. So communities must weigh how great the hazard is, what different In the 1906 San Francisco earthquake, fire was much more destructive than the ground shaking. building strategies cost, and make an informed decision. In 1868 marked the Hayward Fault erupted in what would be a disastrous earthquake today. Since the fault erupts every 140 years on average, East Bay residents and geologists are working to prepare for the inevitable event. Click image to the left or use the URL below. URL: | text | null |
L_0137 | earthquake zones | T_1090 | In a single year, on average, more than 900,000 earthquakes are recorded and 150,000 of them are strong enough to be felt. Each year about 18 earthquakes are major, with a Richter magnitude of 7.0 to 7.9, and on average one earthquake has a magnitude of 8 to 8.9. Magnitude 9 earthquakes are rare. The United States Geological Survey lists five since 1900 (see Figure 1.1 and Table 1.1). All but the Great Indian Ocean Earthquake of 2004 occurred somewhere around the Pacific Ocean basin. Location Valdivia, Chile Prince William Sound, Alaska Great Indian Ocean Earthquake Kamchatka, Alaska Tohoku, Japan Year 1960 1964 2004 1952 2011 Magnitude 9.5 9.2 9.1 9.0 9.0 The 1964 Good Friday Earthquake cen- tered in Prince William Sound, Alaska re- leased the second most amount of energy of any earthquake in recorded history. | text | null |
L_0137 | earthquake zones | T_1091 | Nearly 95% of all earthquakes take place along one of the three types of plate boundaries. About 80% of all earthquakes strike around the Pacific Ocean basin because it is lined with convergent and transform boundaries (Figure 1.2). About 15% take place in the Mediterranean-Asiatic Belt, where convergence is causing the Indian Plate to run into the Eurasian Plate. The remaining 5% are scattered around other plate boundaries or are intraplate earthquakes. Earthquake epicenters for magnitude 8.0 and greater events since 1900. The earthquake depth shows that most large quakes are shallow focus, but some sub- ducted plates cause deep focus quakes. | text | null |
L_0138 | earthquakes at convergent plate boundaries | T_1092 | Earthquakes at convergent plate boundaries mark the motions of subducting lithosphere as it plunges through the mantle (Figure 1.1). Eventually the plate heats up enough deform plastically and earthquakes stop. Convergent plate boundaries produce earthquakes all around the Pacific Ocean basin. | text | null |
L_0138 | earthquakes at convergent plate boundaries | T_1093 | Earthquakes in Japan are caused by ocean-ocean convergence. The Philippine Plate and the Pacific Plate subduct beneath oceanic crust on the North American or Eurasian plates. This complex plate tectonics situation creates a chain of volcanoes, the Japanese islands, and as many as 1,500 earthquakes annually. In March 2011 an enormous 9.0 earthquake struck off of Sendai in northeastern Japan. This quake, called the 2011 Tohoku earthquake, was the most powerful ever to strike Japan and one of the top five known in the world. Damage from the earthquake was nearly overshadowed by the tsunami it generated, which wiped out coastal cities and towns This cross section of earthquake epicen- ters with depth outlines the subducting plate with shallow, intermediate, and deep earthquakes. (Figure 1.2). Several months after the earthquake, about 22,000 people were dead or missing, and 190,000 buildings had been damaged or destroyed. Aftershocks, some as large as major earthquakes, have continued to rock the region. Destruction in Ofunato, Japan, from the 2011 Tohoku Earthquake. | text | null |
L_0138 | earthquakes at convergent plate boundaries | T_1093 | Earthquakes in Japan are caused by ocean-ocean convergence. The Philippine Plate and the Pacific Plate subduct beneath oceanic crust on the North American or Eurasian plates. This complex plate tectonics situation creates a chain of volcanoes, the Japanese islands, and as many as 1,500 earthquakes annually. In March 2011 an enormous 9.0 earthquake struck off of Sendai in northeastern Japan. This quake, called the 2011 Tohoku earthquake, was the most powerful ever to strike Japan and one of the top five known in the world. Damage from the earthquake was nearly overshadowed by the tsunami it generated, which wiped out coastal cities and towns This cross section of earthquake epicen- ters with depth outlines the subducting plate with shallow, intermediate, and deep earthquakes. (Figure 1.2). Several months after the earthquake, about 22,000 people were dead or missing, and 190,000 buildings had been damaged or destroyed. Aftershocks, some as large as major earthquakes, have continued to rock the region. Destruction in Ofunato, Japan, from the 2011 Tohoku Earthquake. | text | null |
L_0138 | earthquakes at convergent plate boundaries | T_1094 | The Pacific Northwest of the United States is at risk from a potentially massive earthquake that could strike any time. The subduction of three small plates beneath North America produces active volcanoes, the Cascades. As with an active subduction zone, there are also earthquakes. Surprisingly, large earthquakes only hit every 300 to 600 years. The last was in 1700, with an estimated magnitude of around 9. A quake of that magnitude today could produce an incredible amount of destruction and untold fatalities. | text | null |
L_0138 | earthquakes at convergent plate boundaries | T_1095 | Massive earthquakes are the hallmark of the thrust faulting and folding when two continental plates converge (Figure injured or homeless. Damage from the 2005 Kashmir earth- quake. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0139 | earthquakes at transform plate boundaries | T_1096 | Deadly earthquakes occur at transform plate boundaries. Transform faults have shallow focus earthquakes. Why do you think this is so? | text | null |
L_0139 | earthquakes at transform plate boundaries | T_1097 | As you learned in the chapter Plate Tectonics, the boundary between the Pacific and North American plates runs through much of California as the San Andreas Fault zone. As you can see in the (Figure 1.1), there is more than just one fault running through the area. There is really a fault zone. The San Andreas Fault runs from south to north up the peninsula, through San Francisco, gets through part of Marin north of the bay, and then goes out to sea. The other faults are part of the fault zone, and they too can be deadly. The faults along the San Andreas Fault zone produce around 10,000 earthquakes a year. Most are tiny, but occasion- ally one is massive. In the San Francisco Bay Area, the Hayward Fault was the site of a magnitude 7.0 earthquake in 1868. The 1906 quake on the San Andreas Fault had a magnitude estimated at about 7.9 (Figure 1.1). About 3,000 people died and 28,000 buildings were lost, mostly in the fire that followed the earthquake. (a) The San Andreas Fault zone in the San Francisco Bay Area. (b) The 1906 San Francisco earthquake is still the most costly natural disaster in California history. Recent California earthquakes occurred in: 1989: Loma Prieta earthquake near Santa Cruz, California. Magnitude 7.1 quake, 63 deaths, 3,756 injuries, 12,000+ people homeless, property damage about $6 billion. 1994: Northridge earthquake on a blind thrust fault near Los Angeles. Magnitude 6.7, 72 deaths, 12,000 injuries, damage estimated at $12.5 billion. In this video, the boundaries between three different tectonic plates and the earthquakes that result from their interactions are explored. Click image to the left or use the URL below. URL: | text | null |
L_0139 | earthquakes at transform plate boundaries | T_1098 | New Zealand also has a transform fault with strike-slip motion, causing about 20,000 earthquakes a year! Only a small percentage of those are large enough to be felt. A 6.3 quake in Christchurch in February 2011 killed about 180 people. | text | null |
L_0141 | earths crust | T_1100 | Earths outer surface is its crust, a cold, thin, brittle outer shell made of rock. The crust is very thin relative to the radius of the planet. There are two very different types of crust, each with its own distinctive physical and chemical properties, which are summarized in Table 1.1. Crust Oceanic Continental Thickness 5-12 km (3-8 mi) Avg. 35 km (22 mi) Density 3.0 g/cm3 2.7 g/cm3 Composition Mafic Felsic Rock types Basalt and gabbro All types | text | null |
L_0141 | earths crust | T_1101 | Oceanic crust is composed of mafic magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro (Figure 1.1). Gabbro from ocean crust. The gabbro is deformed because of intense faulting at the eruption site. Sediments, primarily mud and the shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore, where it comes off the continents in rivers and on wind currents. The oceanic crust is relatively thin and lies above the mantle. The cross section of oceanic crust in the Figure 1.2 shows the layers that grade from sediments at the top to extrusive basalt lava, to the sheeted dikes that feed lava to the surface, to deeper intrusive gabbro, and finally to the mantle. | text | null |
L_0141 | earths crust | T_1102 | Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic rocks of the oceanic crust (Figure 1.3). Because it is thick and has relatively low density, continental crust rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins. When filled with water, these basins form the planets oceans. Click image to the left or use the URL below. URL: A cross-section of oceanic crust. | text | null |
L_0143 | earths layers | T_1112 | The layers scientists recognize are pictured below (Figure 1.1). Core, mantle, and crust are divisions based on composition: 1. The crust is less than 1% of Earth by mass. The two types are oceanic crust and continental crust.Continental crust is felsic and oceanic crust is mafic. 2. The mantle is hot, ultramafic rock. It represents about 68% of Earths mass. 3. The core is mostly iron metal. The core makes up about 31% of the Earth. | text | null |
L_0143 | earths layers | T_1113 | Lithosphere and asthenosphere are divisions based on mechanical properties: 1. The lithosphere is composed of both the crust and the portion of the upper mantle and behaves as a brittle, rigid solid. 2. The asthenosphere is partially molten upper mantle material and behaves plastically and can flow. A cross section of Earth showing the fol- lowing layers: (1) crust (2) mantle (3a) outer core (3b) inner core (4) lithosphere (5) asthenosphere (6) outer core (7) inner core. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0145 | earths mantle | T_1116 | The two most important things about the mantle are: (1) it is made of solid rock, and (2) it is hot. | text | null |
L_0145 | earths mantle | T_1117 | Scientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals (Figure 1.1). Peridotite is rarely found at Earths surface. | text | null |
L_0145 | earths mantle | T_1118 | Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties. Heat flows in two different ways within the Earth: 1. Conduction: Heat is transferred through rapid collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core. Peridotite is formed of crystals of olivine (green) and pyroxene (black). 2. Convection: If a material is able to move, even if it moves very slowly, convection currents can form. Convection in the mantle is the same as convection in a pot of water on a stove. Convection currents within Earths mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. The rising material begins the convection current. When the warm material reaches the surface, it spreads horizontally. The material cools because it is no longer near the core. It eventually becomes cool and dense enough to sink back down into the mantle. At the bottom of the mantle, the material travels horizontally and is heated by the core. It reaches the location where warm mantle material rises, and the mantle convection cell is complete (Figure 1.2). Convection. | text | null |
L_0145 | earths mantle | T_1118 | Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties. Heat flows in two different ways within the Earth: 1. Conduction: Heat is transferred through rapid collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core. Peridotite is formed of crystals of olivine (green) and pyroxene (black). 2. Convection: If a material is able to move, even if it moves very slowly, convection currents can form. Convection in the mantle is the same as convection in a pot of water on a stove. Convection currents within Earths mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. The rising material begins the convection current. When the warm material reaches the surface, it spreads horizontally. The material cools because it is no longer near the core. It eventually becomes cool and dense enough to sink back down into the mantle. At the bottom of the mantle, the material travels horizontally and is heated by the core. It reaches the location where warm mantle material rises, and the mantle convection cell is complete (Figure 1.2). Convection. | text | null |
L_0147 | earths tectonic plates | T_1120 | What portion of Earth makes up the plates in plate tectonics? Again, the answer came about in part due to war. In this case, the Cold War. During the 1950s and early 1960s, scientists set up seismograph networks to see if enemy nations were testing atomic bombs. These seismographs also recorded all of the earthquakes around the planet. The seismic records were used to locate an earthquakes epicenter, the point on Earths surface directly above the place where the earthquake occurs. Why is this relevant? It turns out that earthquake epicenters outline the plates. This is because earthquakes occur everywhere plates come into contact with each other. The lithosphere is divided into a dozen major and several minor plates (Figure 1.1). A single plate can be made of all oceanic lithosphere or all continental lithosphere, but nearly all plates are made of a combination of both. The movement of the plates over Earths surface is termed plate tectonics. Plates move at a rate of a few centimeters a year, about the same rate fingernails grow. | text | null |
L_0147 | earths tectonic plates | T_1121 | If seafloor spreading drives the plates, what drives seafloor spreading? This goes back to Arthur Holmes idea of mantle convection. Picture two convection cells side by side in the mantle, similar to the illustration in Figure 1.2. 1. Hot mantle from the two adjacent cells rises at the ridge axis, creating new ocean crust. 2. The top limb of the convection cell moves horizontally away from the ridge crest, as does the new seafloor. 3. The outer limbs of the convection cells plunge down into the deeper mantle, dragging oceanic crust as well. This takes place at the deep sea trenches. 4. The material sinks to the core and moves horizontally. 5. The material heats up and reaches the zone where it rises again. | text | null |
L_0147 | earths tectonic plates | T_1122 | Plate boundaries are the edges where two plates meet. How can two plates move relative to each other? Most geologic activities, including volcanoes, earthquakes, and mountain building, take place at plate boundaries. The features found at these plate boundaries are the mid-ocean ridges, trenches, and large transform faults (Figure 1.3). Divergent plate boundaries: the two plates move away from each other. Convergent plate boundaries: the two plates move towards each other. Transform plate boundaries: the two plates slip past each other. The type of plate boundary and the type of crust found on each side of the boundary determines what sort of geologic activity will be found there. We can visit each of these types of plate boundaries on land or at sea. | text | null |
L_0153 | effusive eruptions | T_1136 | Mafic magma creates gentler effusive eruptions. Although the pressure builds enough for the magma to erupt, it does not erupt with the same explosive force as felsic magma. Magma pushes toward the surface through fissures. Eventually, the magma reaches the surface and erupts through a vent (Figure 1.1). Effusive eruptions are common in Hawaii, where lavas are mafic. In effusive eruptions, lava flows readily, producing rivers of molten rock. A Quicktime movie with thermal camera of a lava stream within the vent of a Hawaiian volcano is seen here: | text | null |
L_0153 | effusive eruptions | T_1137 | Low-viscosity lava flows down mountainsides. Differences in composition and where the lavas erupt result in three types of lava flow coming from effusive eruptions. Aa lava forms a thick and brittle crust that is torn into rough and jagged pieces. Aa lava can spread over large areas as the lava continues to flow underneath the crusts surface. Pahoehoe lava forms lava tubes where fluid lava flows through the outer cooled rock crust. Pahoehoe lava is less viscous than aa lava, so its surface looks is smooth and ropy. Mafic lava that erupts underwater creates pillow lava. The lava cools very quickly, forming roughly spherical rocks. Pillow lava is common at mid-ocean ridges (Figure (a) Aa lava spread over large areas. (b) Pahoehoe lava tubes where at the Thurston Lava Tube in Hawaii Volcanoes National Park. (c) Pahoehoe lava is less viscous than aa lava so its surface looks is smooth and ropy. (d) Pillow lava. | text | null |
L_0153 | effusive eruptions | T_1138 | People can usually be evacuated before an effusive eruption, so they are much less deadly. Although effusive eruptions rarely kill anyone, they can be destructive. Even when people know that a lava flow is approaching, there is not much anyone can do to stop it from destroying a building or road (Figure 1.3). | text | null |
L_0159 | evolution of simple cells | T_1149 | Simple organic molecules such as proteins and nucleic acids eventually became complex organic substances. Sci- entists think that the organic molecules adhered to clay minerals, which provided the structure needed for these substances to organize. The clays, along with their metal cations, catalyzed the chemical reactions that caused the molecules to form polymers. The first RNA fragments could also have come together on ancient clays. E. coli (Escherichia coli) is a primitive prokaryote that may resemble the earliest cells. For an organic molecule to become a cell, it must be able to separate itself from its environment. To enclose the molecule, a lipid membrane grew around the organic material. Eventually the molecules could synthesize their own organic material and replicate themselves. These became the first cells. | text | null |
L_0159 | evolution of simple cells | T_1150 | The earliest cells were prokaryotes (Figure 1.1). Although prokaryotes have a cell membrane, they lack a cell nucleus and other organelles. Without a nucleus, RNA was loose within the cell. Over time the cells became more complex. LUCA was a prokaryote but differed from the first living cells because its genetic code was based on DNA. The oldest fossils are tiny microbe-like objects that are 3.5 billion years old. Evidence for bacteria, the first single-celled life forms, goes back 3.5 billion years (Figure 1.2). | text | null |
L_0159 | evolution of simple cells | T_1151 | The earliest life forms did not have the ability to photosynthesize. Without photosynthesis what did the earliest cells eat? Most likely they absorbed the nutrients that floated around in the organic soup that surrounded them. After hundreds of millions of years, these nutrients would have become less abundant. Sometime around 3 billion years ago (about 1.5 billion years after Earth formed!), photosynthesis began. Photo- synthesis allowed organisms to use sunlight and inorganic molecules, such as carbon dioxide and water, to create chemical energy that they could use for food. To photosynthesize, a cell needs chloroplasts (Figure 1.3). A diagram of a bacterium. Chloroplasts are visible in these cells found within a moss. | text | null |
L_0159 | evolution of simple cells | T_1151 | The earliest life forms did not have the ability to photosynthesize. Without photosynthesis what did the earliest cells eat? Most likely they absorbed the nutrients that floated around in the organic soup that surrounded them. After hundreds of millions of years, these nutrients would have become less abundant. Sometime around 3 billion years ago (about 1.5 billion years after Earth formed!), photosynthesis began. Photo- synthesis allowed organisms to use sunlight and inorganic molecules, such as carbon dioxide and water, to create chemical energy that they could use for food. To photosynthesize, a cell needs chloroplasts (Figure 1.3). A diagram of a bacterium. Chloroplasts are visible in these cells found within a moss. | text | null |
L_0159 | evolution of simple cells | T_1152 | In what two ways did photosynthesis make the planet much more favorable for life? 1. Photosynthesis allowed organisms to create food energy so that they did not need to rely on nutrients floating around in the environment. Photosynthesizing organisms could also become food for other organisms. 2. A byproduct of photosynthesis is oxygen. When photosynthesis evolved, all of a sudden oxygen was present in large amounts in the atmosphere. For organisms used to an anaerobic environment, the gas was toxic, and many organisms died out. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0159 | evolution of simple cells | T_1153 | What were these organisms that completely changed the progression of life on Earth by changing the atmosphere from anaerobic to aerobic? The oldest known fossils that are from organisms known to photosynthesize are cyanobac- teria. Cyanobacteria were present by 2.8 billion years ago, and some may have been around as far back as 3.5 billion years. Cyanobacteria were the dominant life forms in the Archean. Why would such a primitive life-form have been dominant in the Precambrian? Many cyanobacteria lived in reef-like structures known as stromatolites (Figure These rocks in Glacier National Park, Montana may contain some of the oldest fossil microbes on Earth. Modern cyanobacteria are also called blue-green algae. These organisms may consist of a single or many cells and they are found in many different environments (Figure 1.5). Even now cyanobacteria account for 20% to 30% of photosynthesis on Earth. A large bloom of cyanobacteria is harmful to this lake. | text | null |
L_0159 | evolution of simple cells | T_1153 | What were these organisms that completely changed the progression of life on Earth by changing the atmosphere from anaerobic to aerobic? The oldest known fossils that are from organisms known to photosynthesize are cyanobac- teria. Cyanobacteria were present by 2.8 billion years ago, and some may have been around as far back as 3.5 billion years. Cyanobacteria were the dominant life forms in the Archean. Why would such a primitive life-form have been dominant in the Precambrian? Many cyanobacteria lived in reef-like structures known as stromatolites (Figure These rocks in Glacier National Park, Montana may contain some of the oldest fossil microbes on Earth. Modern cyanobacteria are also called blue-green algae. These organisms may consist of a single or many cells and they are found in many different environments (Figure 1.5). Even now cyanobacteria account for 20% to 30% of photosynthesis on Earth. A large bloom of cyanobacteria is harmful to this lake. | text | null |
L_0163 | explosive eruptions | T_1162 | A large explosive eruption creates even more devastation than the force of the atom bomb dropped on Nagasaki at the end of World War II, in which more than 40,000 people died. A large explosive volcanic eruption is 10,000 times as powerful. Explosive eruptions are found at the convergent plate boundaries that line parts of western North America, resulting in the Cascades in the Pacific Northwest and the Aleutians in Alaska. | text | null |
L_0163 | explosive eruptions | T_1163 | Explosive eruptions are caused by gas-rich, felsic magmas that churn within the magma chamber. When the pressure becomes too great the magma breaks through the rock above the chamber and explodes, just like when a cork is released from a bottle of champagne. Magma, rock, and ash burst upward in an enormous explosion (Figure 1.1). | text | null |
L_0163 | explosive eruptions | T_1164 | The erupted rock fragments are called tephra. Ash and gas also explode from the volcano. Scorching hot tephra, ash, and gas may speed down the volcanos slopes at 700 km/h (450 mph) as a pyroclastic flow. Pyroclastic means fire rock (Figure 1.2). Left: An explosive eruption from the Mayon Volcano in the Philippines in 1984. Ash flies upward into the sky and pyroclastic flows pour down the mountainside. Right: The end of a pyroclastic flow at Mount St. Helens. Pyroclastic flows knock down everything in their path. The temperature inside a pyroclastic flow may be as high as 1,000 C (1,800 F). Blowdown of trees near Mount St. Helens shows the direction of the blast and pyro- clastic flow. | text | null |
L_0163 | explosive eruptions | T_1164 | The erupted rock fragments are called tephra. Ash and gas also explode from the volcano. Scorching hot tephra, ash, and gas may speed down the volcanos slopes at 700 km/h (450 mph) as a pyroclastic flow. Pyroclastic means fire rock (Figure 1.2). Left: An explosive eruption from the Mayon Volcano in the Philippines in 1984. Ash flies upward into the sky and pyroclastic flows pour down the mountainside. Right: The end of a pyroclastic flow at Mount St. Helens. Pyroclastic flows knock down everything in their path. The temperature inside a pyroclastic flow may be as high as 1,000 C (1,800 F). Blowdown of trees near Mount St. Helens shows the direction of the blast and pyro- clastic flow. | text | null |
L_0163 | explosive eruptions | T_1165 | Prior to the Mount St. Helens eruption in 1980, the Lassen Peak eruption on May 22, 1915, was the most recent Cascades eruption. A column of ash and gas shot 30,000 feet into the air. This triggered a high-speed pyroclastic flow, which melted snow and created a volcanic mudflow known as a lahar. Lassen Peak currently has geothermal activity and could erupt explosively again. Mt. Shasta, the other active volcano in California, erupts every 600 to 800 years. An eruption would most likely create a large pyroclastic flow, and probably a lahar. Of course, Mt. Shasta could explode and collapse like Mt. Mazama in Oregon (Figure 1.4). Crater Lake fills the caldera of the col- lapsed Mt. Mazama, which erupted with 42 times more power than Mount St. He- lens in 1980. The bathymetry of the lake shows volcanic features such as cinder cones. | text | null |
L_0163 | explosive eruptions | T_1166 | Volcanic gases can form poisonous and invisible clouds in the atmosphere. These gases may contribute to environ- mental problems such as acid rain and ozone destruction. Particles of dust and ash may stay in the atmosphere for years, disrupting weather patterns and blocking sunlight (Figure 1.5). The ash plume from Eyjafjallajkull vol- cano in Iceland disrupted air travel across Europe for six days in April 2010. Click image to the left or use the URL below. URL: | text | null |
L_0166 | finding and mining ores | T_1174 | Some minerals are very useful. An ore is a rock that contains minerals with useful elements. Aluminum in bauxite ore (Figure 1.1) is extracted from the ground and refined to be used in aluminum foil and many other products. The cost of creating a product from a mineral depends on how abundant the mineral is and how much the extraction and refining processes cost. Environmental damage from these processes is often not figured into a products cost. It is important to use mineral resources wisely. | text | null |
L_0166 | finding and mining ores | T_1175 | Geologic processes create and concentrate minerals that are valuable natural resources. Geologists study geological formations and then test the physical and chemical properties of soil and rocks to locate possible ores and determine their size and concentration. A mineral deposit will only be mined if it is profitable. A concentration of minerals is only called an ore deposit if it is profitable to mine. There are many ways to mine ores. Aluminum is made from the aluminum- bearing minerals in bauxite. | text | null |
L_0166 | finding and mining ores | T_1176 | Surface mining allows extraction of ores that are close to Earths surface. Overlying rock is blasted and the rock that contains the valuable minerals is placed in a truck and taken to a refinery. As pictured in Figure 1.2, surface mining includes open-pit mining and mountaintop removal. Other methods of surface mining include strip mining, placer mining, and dredging. Strip mining is like open pit mining but with material removed along a strip. These different forms of surface mining are methods of extracting ores close to Earths surface. Placers are valuable minerals found in stream gravels. Californias nickname, the Golden State, can be traced back to the discovery of placer deposits of gold in 1848. The gold weathered out of hard metamorphic rock in the western Sierra Nevada, which also contains deposits of copper, lead, zinc, silver, chromite, and other valuable minerals. The | text | null |
L_0166 | finding and mining ores | T_1177 | Underground mining is used to recover ores that are deeper into Earths surface. Miners blast and tunnel into rock to gain access to the ores. How underground mining is approached from above, below, or sideways depends on the placement of the ore body, its depth, the concentration of ore, and the strength of the surrounding rock. Underground mining is very expensive and dangerous. Fresh air and lights must also be brought into the tunnels for the miners, and accidents are far too common. | text | null |
L_0166 | finding and mining ores | T_1178 | The ores journey to becoming a useable material is only just beginning when the ore leaves the mine (Figure separated out of the ore. A few methods for extracting ore are: heap leaching: the addition of chemicals, such as cyanide or acid, to remove ore. flotation: the addition of a compound that attaches to the valuable mineral and floats. smelting: roasting rock, causing it to segregate into layers so the mineral can be extracted. To extract the metal from the ore, the rock is melted at a temperature greater than 900o C, which requires a lot of energy. Extracting metal from rock is so energy-intensive that if you recycle just 40 aluminum cans, you will save the energy equivalent of one gallon of gasoline. | text | null |
L_0209 | intraplate activity | T_1333 | A small amount of geologic activity, known as intraplate activity, does not take place at plate boundaries but within a plate instead. Mantle plumes are pipes of hot rock that rise through the mantle. The release of pressure causes melting near the surface to form a hotspot. Eruptions at the hotspot create a volcano. Hotspot volcanoes are found in a line (Figure 1.1). Can you figure out why? Hint: The youngest volcano sits above the hotspot and volcanoes become older with distance from the hotspot. | text | null |
L_0209 | intraplate activity | T_1334 | The first photo above is of a volcanic eruption in Hawaii. Hawaii is not in western North America, but is in the central Pacific ocean, near the middle of the Pacific Plate. The Hawaiian Islands are a beautiful example of a hotspot chain in the Pacific Ocean. Kilauea volcano lies above the Hawaiian hotspot. Mauna Loa volcano is older than Kilauea and is still erupting, but at a slower rate. The islands get progressively older to the northwest because they are further from the hotspot. This is because the Pacific Plate is moving toward the northwest over the hotspot. Loihi, the youngest volcano, is still below the sea surface. Since many hotspots are stationary in the mantle, geologists can use some hotspot chains to tell the direction and the speed a plate is moving (Figure 1.2). The Hawaiian chain continues into the Emperor Seamounts. The bend in the chain was caused by a change in the direction of the Pacific Plate 43 million years ago. Using the age and distance of the bend, geologists can figure out the speed of the Pacific Plate over the hotspot. The Hawaiian Islands have formed from volcanic eruptions above the Hawaii hotspot. | text | null |
L_0209 | intraplate activity | T_1334 | The first photo above is of a volcanic eruption in Hawaii. Hawaii is not in western North America, but is in the central Pacific ocean, near the middle of the Pacific Plate. The Hawaiian Islands are a beautiful example of a hotspot chain in the Pacific Ocean. Kilauea volcano lies above the Hawaiian hotspot. Mauna Loa volcano is older than Kilauea and is still erupting, but at a slower rate. The islands get progressively older to the northwest because they are further from the hotspot. This is because the Pacific Plate is moving toward the northwest over the hotspot. Loihi, the youngest volcano, is still below the sea surface. Since many hotspots are stationary in the mantle, geologists can use some hotspot chains to tell the direction and the speed a plate is moving (Figure 1.2). The Hawaiian chain continues into the Emperor Seamounts. The bend in the chain was caused by a change in the direction of the Pacific Plate 43 million years ago. Using the age and distance of the bend, geologists can figure out the speed of the Pacific Plate over the hotspot. The Hawaiian Islands have formed from volcanic eruptions above the Hawaii hotspot. | text | null |
L_0209 | intraplate activity | T_1335 | The second photo in the introduction is of a geyser at Yellowstone National Park in Wyoming. Yellowstone is in the western U.S. but is inland from the plate boundaries offshore. Hotspot magmas rarely penetrate through thick continental crust, so hotspot activity on continents is rare. One exception is the Yellowstone hotspot (Figure 1.3). Volcanic activity above the Yellowstone hotspot on can be traced from 15 million years ago to its present location on the North American Plate. The ages of volcanic activity attributed to the Yellowstone hotspot. Click image to the left or use the URL below. URL: | text | null |
L_0210 | intraplate earthquakes | T_1336 | Intraplate earthquakes are the result of stresses caused by plate motions acting in solid slabs of lithosphere. The earthquakes take place along ancient faults or rift zones that have been weakened by activity that may have taken place hundreds of millions of years ago. | text | null |
L_0210 | intraplate earthquakes | T_1337 | In August 2011 the eastern seaboard of the U.S. was rocked by a magnitude 5.8 earthquake. While not huge, most of the residents had never experienced a quake and many didnt know what it was. Some people thought the shaking might have been the result of a terrorist attack. This region is no longer part of an active plate boundary. But if you went back in time to the late Paleozoic, you would find the region being uplifted into the ancestral Appalachian mountains as continent-continent convergence brought Pangaea together. The Piedmont Seismic Zone is an area of several hundred million year-old faults that sometimes reactivate. | text | null |
L_0210 | intraplate earthquakes | T_1338 | In 1812, a magnitude 7.5 earthquake struck near New Madrid, Missouri. The earthquake was strongly felt over approximately 50,000 square miles and altered the course of the Mississippi River. Because very few people lived there at the time, only 20 people died. Many more people live there today (Figure 1.1). A similar earthquake today would undoubtedly kill many people and cause a great deal of property damage. Like the Piedmont Seismic Zone, the New Madrid Seismic Zone is a set of reactivated faults. These faults are left from the rifting apart of the supercontinent Rodinia about 750 million years ago. The plates did not rift apart here but left a weakness in the lithosphere that makes the region vulnerable to earthquakes. Click image to the left or use the URL below. URL: | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1349 | Gravity shapes the Earths surface by moving weathered material from a higher place to a lower one. This occurs in a variety of ways and at a variety of rates, including sudden, dramatic events as well as slow, steady movements that happen over long periods of time. The force of gravity is constant and it is changing the Earths surface right now. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1350 | Erosion by gravity is called mass wasting. Mass wasting can be slow and virtually imperceptible, or rapid, massive, and deadly. Weathered material may fall away from a cliff because there is nothing to keep it in place. Rocks that fall to the base of a cliff make a talus slope. Sometimes as one rock falls, it hits another rock, which hits another rock, and begins a landslide. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1351 | Landslides are the most dramatic, sudden, and dangerous examples of Earth materials moved by gravity. Landslides are sudden falls of rock; by contrast, avalanches are sudden falls of snow. When large amounts of rock suddenly break loose from a cliff or mountainside, they move quickly and with tremendous force (Figure 1.1). Air trapped under the falling rocks acts as a cushion that keeps the rock from slowing down. Landslides can move as fast as 200 to 300 km/hour. This landslide in California in 2008 blocked Highway 140. Landslides are exceptionally destructive. Homes may be destroyed as hillsides collapse. Landslides can even bury entire villages. Landslides may create lakes when the rocky material dams a stream. If a landslide flows into a lake or bay, they can trigger a tsunami. Landslides often occur on steep slopes in dry or semi-arid climates. The California coastline, with its steep cliffs and years of drought punctuated by seasons of abundant rainfall, is prone to landslides. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1352 | Added water creates natural hazards produced by gravity (Figure 1.2). On hillsides with soils rich in clay, little rain, and not much vegetation to hold the soil in place, a time of high precipitation will create a mudflow. Mudflows follow river channels, washing out bridges, trees, and homes that are in their path. A lahar is mudflow that flows down a composite volcano (Figure 1.3). Ash mixes with snow and ice melted by the eruption to produce hot, fast-moving flows. The lahar caused by the eruption of Nevado del Ruiz in Columbia in 1985 killed more than 23,000 people. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1353 | Less dramatic types of downslope movement move Earth materials slowly down a hillside. Slump moves materials as a large block along a curved surface (Figure 1.4). Slumps often happen when a slope is undercut, with no support for the overlying materials, or when too much weight is added to an unstable slope. Mudflows are common in southern California. A lahar is a mudflow that forms from vol- canic ash and debris. Slump material moves as a whole unit, leaving behind a crescent shaped scar. The trunks of these trees near Mineral King, California, were bent by snow creeping downhill when the trees were saplings. Click image to the left or use the URL below. URL: | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1353 | Less dramatic types of downslope movement move Earth materials slowly down a hillside. Slump moves materials as a large block along a curved surface (Figure 1.4). Slumps often happen when a slope is undercut, with no support for the overlying materials, or when too much weight is added to an unstable slope. Mudflows are common in southern California. A lahar is a mudflow that forms from vol- canic ash and debris. Slump material moves as a whole unit, leaving behind a crescent shaped scar. The trunks of these trees near Mineral King, California, were bent by snow creeping downhill when the trees were saplings. Click image to the left or use the URL below. URL: | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1353 | Less dramatic types of downslope movement move Earth materials slowly down a hillside. Slump moves materials as a large block along a curved surface (Figure 1.4). Slumps often happen when a slope is undercut, with no support for the overlying materials, or when too much weight is added to an unstable slope. Mudflows are common in southern California. A lahar is a mudflow that forms from vol- canic ash and debris. Slump material moves as a whole unit, leaving behind a crescent shaped scar. The trunks of these trees near Mineral King, California, were bent by snow creeping downhill when the trees were saplings. Click image to the left or use the URL below. URL: | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1353 | Less dramatic types of downslope movement move Earth materials slowly down a hillside. Slump moves materials as a large block along a curved surface (Figure 1.4). Slumps often happen when a slope is undercut, with no support for the overlying materials, or when too much weight is added to an unstable slope. Mudflows are common in southern California. A lahar is a mudflow that forms from vol- canic ash and debris. Slump material moves as a whole unit, leaving behind a crescent shaped scar. The trunks of these trees near Mineral King, California, were bent by snow creeping downhill when the trees were saplings. Click image to the left or use the URL below. URL: | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1354 | There are several factors that increase the chance that a landslide will occur. Some of these we can prevent and some we cannot. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1355 | A little bit of water helps to hold grains of sand or soil together. For example, you can build a larger sand castle with slightly wet sand than with dry sand. However, too much water causes the sand to flow quickly away. Rapid snow melt or rainfall adds extra water to the soil, which increases the weight of the slope and makes sediment grains lose contact with each other, allowing flow. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1356 | Layers of weak rock, such as clay, also allow more landslides. Wet clay is very slippery, which provides an easy surface for materials to slide over. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1357 | If people dig into the base of a slope to create a road or a homesite, the slope may become unstable and move downhill. This is particularly dangerous when the underlying rock layers slope towards the area. When construction workers cut into slopes for homes or roads, they must stabilize the slope to help prevent a landslide (Figure 1.6). Tree roots or even grasses can bind soil together. It is also a good idea to provide drainage so that the slope does not become saturated with water. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1358 | An earthquake, volcanic eruption, or even just a truck going by can shake unstable ground loose and cause a slide. Skiers and hikers may disturb the snow they travel over and set off an avalanche. | text | null |
L_0214 | landforms from erosion and deposition by gravity | T_1359 | Landslides cause $1 billion to $2 billion damage in the United States each year and are responsible for traumatic and sudden loss of life and homes in many areas of the world. Some at-risk communities have developed landslide warning systems. Around San Francisco Bay, the National Weather Service and the U.S. Geological Survey use rain gauges to monitor soil moisture. If soil becomes saturated, the weather service issues a warning. Earthquakes, which may occur on Californias abundant faults, can also trigger landslides. To be safe from landslides: Be aware of your surroundings and notice changes in the natural world. Look for cracks or bulges in hillsides, tilting of decks or patios, or leaning poles or fences when rainfall is heavy. Sticking windows and doors can indicate ground movement as soil pushes slowly against a house and knocks windows and doors out of alignment. Look for landslide scars because landslides are most likely to happen where they have occurred before. Plant vegetation and trees on the hillside around your home to help hold soil in place. Help to keep a slope stable by building retaining walls. Installing good drainage in a hillside may keep the soil from getting saturated. Hillside properties in the San Francisco Bay Area and elsewhere may be prone to damage from landslides. Geologists are studying the warning signs and progress of local landslides to help reduce risks and give people adequate warnings of these looming threats. | text | null |
L_0218 | lithosphere and asthenosphere | T_1370 | The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid. The lithosphere is about 100 kilometers thick. How are crust and lithosphere different from each other? The definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake. Although we sometimes refer to Earths plates as being plates of crust, the plates are actually made of lithosphere. Much more about Earths plates follows in the chapter "Plate Tectonics." | text | null |
L_0218 | lithosphere and asthenosphere | T_1371 | The asthenosphere is solid upper mantle material that is so hot that it behaves plastically and can flow. The lithosphere rides on the asthenosphere. | text | null |
L_0220 | locating earthquake epicenters | T_1380 | Here are the steps to finding an earthquake epicenter using three seismograms: 1. Determine the epicenter distance from three different seismographs. The longer the time between the arrival of the P-wave and S-wave, the farther away is the epicenter. So the difference in the P- and S-wave arrival times determines the distance between the epicenter and a seismometer. 2. Draw a circle with a radius equal to the distance from the epicenter for that seismograph. The epicenter is somewhere along that circle. Do this for three locations. Using data from two seismographs, the two circles will intercept at two points. A third circle will intercept the other two circles at a single point. This point is the earthquake epicenter (Figure 1.1). Of course, its been a long time since scientists drew circles to locate an earthquake epicenter. This is all done digitally now. but its a great way to learn the basics of how locating an epicenter works. Three circles drawn from three seismic stations each equal to the radius from the station to the epicenter of the quake will intercept at the actual epicenter. Click image to the left or use the URL below. URL: | text | null |
L_0223 | magma composition at volcanoes | T_1392 | There are as many types of volcanic eruptions as there are eruptions. Actually more since an eruption can change character as it progresses. Each volcanic eruption is unique, differing in size, style, and composition of erupted material. One key to what makes the eruption unique is the chemical composition of the magma that feeds a volcano, which determines (1) the eruption style, (2) the type of volcanic cone that forms, and (3) the composition of rocks that are found at the volcano. Different minerals within a rock melt at different temperatures. The amount of partial melting and the composition of the original rock determine the composition of the magma. The words that describe composition of igneous rocks also describe magma composition. Mafic magmas are low in silica and contain more dark, magnesium- and iron-rich mafic minerals, such as olivine and pyroxene. Felsic magmas are higher in silica and contain lighter colored minerals such as quartz and orthoclase feldspar. The higher the amount of silica in the magma, the higher is its viscosity. Viscosity is a liquids resistance to flow. Viscosity determines what the magma will do. Mafic magma is not viscous and will flow easily to the surface. Felsic magma is viscous and does not flow easily. Most felsic magma will stay deeper in the crust and will cool to form igneous intrusive rocks such as granite and granodiorite. If felsic magma rises into a magma chamber, it may be too viscous to move, so it gets stuck. Dissolved gases become trapped by thick magma. The magma churns in the chamber and the pressure builds. Magma collects in magma chambers in the crust at 160 kilometers (100 miles) beneath the surface. Click image to the left or use the URL below. URL: | text | null |
L_0228 | materials humans use | T_1407 | People depend on natural resources for just about everything that keeps us fed and sheltered, as well as for the things that keep us entertained. Every person in the United States uses about 20,000 kilograms (40,000 pounds) of minerals every year for a wide range of products, such as cell phones, TVs, jewelry, and cars. Table 1.1 shows some common objects, the materials they are made from, and whether they are renewable or non-renewable. Common Object Natural Resources Used Cars 15 different metals, such as iron, lead, and chromium to make the body. Precious metals like gold, silver, and platinum. Gems like diamonds, rubies, emer- alds, turquoise. Jewelry Are These Resources Renewable or Non-Renewable? Non-renewable Non-renewable Common Object Natural Resources Used Electronic Appliances (TVs, com- puters, DVD players, cell phones, etc.) Clothing Many different metals, like copper, mercury, gold. Food Bottled Water Gasoline Household Electricity Paper Houses Soil to grow fibers such as cotton. Sunlight for the plants to grow. Animals for fur and leather. Soil to grow plants. Wildlife and agricultural animals. Water from streams or springs. Petroleum products to make plastic bottles. Petroleum drilled from wells. Coal, natural gas, solar power, wind power, hydroelectric power. Trees; Sunlight Soil. Trees for timber. Rocks and minerals for construc- tion materials, for example, granite, gravel, sand. Are These Resources Renewable or Non-Renewable? Non-renewable Renewable Renewable Non-renewable and Renewable Non-renewable Non-renewable and Renewable Renewable Non-renewable and Renewable Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: | text | null |
L_0234 | mesozoic plate tectonics | T_1424 | As heat builds up beneath a supercontinent, continental rifting begins. Basaltic lavas fill in the rift and eventually lead to seafloor spreading and the formation of a new ocean basin. This basalt province is where Africa is splitting apart and generating basalt lava. | text | null |
L_0234 | mesozoic plate tectonics | T_1425 | At the end of the Paleozoic there was one continent and one ocean. When Pangaea began to break apart about 180 million years ago, the Panthalassa Ocean separated into the individual but interconnected oceans that we see today on Earth. The Atlantic Ocean basin formed as Pangaea split apart. The seafloor spreading that pushed Africa and South America apart is continuing to enlarge the Atlantic Ocean (Figure 1.1). As the continents moved apart there was an intense period of plate tectonic activity. Seafloor spreading was so vig- orous that the mid-ocean ridge buoyed upwards and displaced so much water that there was a marine transgression. Later in the Mesozoic those seas regressed and then transgressed again. | text | null |
L_0234 | mesozoic plate tectonics | T_1426 | The moving continents collided with island arcs and microcontinents so that mountain ranges accreted onto the continents edges. The subduction of the oceanic Farallon plate beneath western North America during the late In the Afar Region of Ethiopia, Africa is splitting apart. Three plates are pulling away from a central point. Jurassic and early Cretaceous produced igneous intrusions and other structures. The intrusions have since been uplifted so that they are exposed in the Sierra Nevada Mountains (Figure 1.2). The snow-covered Sierra Nevada is seen striking SE to NW across the eastern third of the image. The mountain range is a line of uplifted batholiths from Mesozoic subduction. Click image to the left or use the URL below. URL: | text | null |
L_0234 | mesozoic plate tectonics | T_1426 | The moving continents collided with island arcs and microcontinents so that mountain ranges accreted onto the continents edges. The subduction of the oceanic Farallon plate beneath western North America during the late In the Afar Region of Ethiopia, Africa is splitting apart. Three plates are pulling away from a central point. Jurassic and early Cretaceous produced igneous intrusions and other structures. The intrusions have since been uplifted so that they are exposed in the Sierra Nevada Mountains (Figure 1.2). The snow-covered Sierra Nevada is seen striking SE to NW across the eastern third of the image. The mountain range is a line of uplifted batholiths from Mesozoic subduction. Click image to the left or use the URL below. URL: | text | null |
L_0235 | metabolism and replication | T_1427 | Organic molecules must also carry out the chemical work of cells; that is, their metabolism. Chemical reactions in a living organism allow that organism to live in its environment, grow, and reproduce. Metabolism gets energy from other sources and creates structures needed in cells. The chemical reactions occur in a sequence of steps known as metabolic pathways. The metabolic pathways are very similar between unicellular bacteria that have been around for billions of years and the most complex life forms on Earth today. This means that they evolved very early in Earths history. | text | null |
L_0235 | metabolism and replication | T_1428 | Living cells need organic molecules, known as nucleic acids, to store genetic information and pass it to the next generation. Deoxyribonucleic acid (DNA) is the nucleic acid that carries information for nearly all living cells today and did for most of Earths history. Ribonucleic acid (RNA) delivers genetic instructions to the location in a cell where protein is synthesized. | text | null |
L_0235 | metabolism and replication | T_1429 | Many scientists think that RNA was the first replicator. Since RNA catalyzes protein synthesis, most scientists think that RNA came before proteins. RNA can also encode genetic instructions and carry it to daughter cells, such as DNA. The idea that RNA is the most primitive organic molecule is called the RNA world hypothesis, referring to the possibility that the RNA is more ancient than DNA. RNA can pass along genetic instructions as DNA can, and some RNA can carry out chemical reactions like proteins can. Click image to the left or use the URL below. URL: Pieces of many scenarios can be put together to come up with a plausible suggestion for how life began. Click image to the left or use the URL below. URL: | text | null |
L_0241 | mineral formation | T_1441 | Minerals form in a variety of ways: crystallization from magma precipitation from ions in solution biological activity a change to a more stable state as in metamorphism precipitation from vapor | text | null |
L_0241 | mineral formation | T_1442 | Imagine a rock that becomes so hot it melts. Many minerals start out in liquids that are hot enough to melt rocks. Magma is melted rock inside Earth, a molten mixture of substances that can be hotter than 1,000 C. Magma cools slowly inside Earth, which gives mineral crystals time to grow large enough to be seen clearly (Figure 1.1). Granite is rock that forms from slowly cooled magma, containing the minerals quartz (clear), plagioclase feldspar (shiny white), potassium feldspar (pink), and bi- otite (black). When magma erupts onto Earths surface, it is called lava. Lava cools much more rapidly than magma. Crystals do not have time to form and are very small. The chemical composition between minerals that form rapidly or slowly is often the same, only their size differs. Existing rocks may be heated enough so that the molecules are released from their structure and can move around. The molecules may match up with different molecules to form new minerals as the rock cools. This occurs during metamorphism, which will be discussed in the "Metamorphic Rocks" concept. | text | null |
L_0241 | mineral formation | T_1443 | Water on Earth, such as the water in the oceans, contains chemical elements mixed into a solution. Various processes can cause these elements to combine to form solid mineral deposits. | text | null |
L_0241 | mineral formation | T_1444 | When water evaporates, it leaves behind a solid precipitate of minerals, as shown in Figure 1.2. When the water in glass A evaporates, the dissolved mineral particles are left behind. Water can only hold a certain amount of dissolved minerals and salts. When the amount is too great to stay dissolved in the water, the particles come together to form mineral solids, which sink. Halite easily precipitates out of water, as does calcite. Some lakes, such as Mono Lake in California (Figure 1.3) or The Great Salt Lake in Utah, contain many mineral precipitates. Tufa towers form when calcium-rich spring water at the bottom of Mono Lake bubbles up into the alkaline lake. The tufa towers appear when lake level drops. | text | null |
L_0241 | mineral formation | T_1444 | When water evaporates, it leaves behind a solid precipitate of minerals, as shown in Figure 1.2. When the water in glass A evaporates, the dissolved mineral particles are left behind. Water can only hold a certain amount of dissolved minerals and salts. When the amount is too great to stay dissolved in the water, the particles come together to form mineral solids, which sink. Halite easily precipitates out of water, as does calcite. Some lakes, such as Mono Lake in California (Figure 1.3) or The Great Salt Lake in Utah, contain many mineral precipitates. Tufa towers form when calcium-rich spring water at the bottom of Mono Lake bubbles up into the alkaline lake. The tufa towers appear when lake level drops. | text | null |
L_0241 | mineral formation | T_1445 | Magma heats nearby underground water, which reacts with the rocks around it to pick up dissolved particles. As the water flows through open spaces in the rock and cools, it deposits solid minerals. The mineral deposits that form when a mineral fills cracks in rocks are called veins (Figure 1.4). Quartz veins formed in this rock. When minerals are deposited in open spaces, large crystals form (Figure 1.5). Amethyst formed when large crystals grew in open spaces inside the rock. These special rocks are called geodes. | text | null |
L_0241 | mineral formation | T_1445 | Magma heats nearby underground water, which reacts with the rocks around it to pick up dissolved particles. As the water flows through open spaces in the rock and cools, it deposits solid minerals. The mineral deposits that form when a mineral fills cracks in rocks are called veins (Figure 1.4). Quartz veins formed in this rock. When minerals are deposited in open spaces, large crystals form (Figure 1.5). Amethyst formed when large crystals grew in open spaces inside the rock. These special rocks are called geodes. | text | null |
L_0241 | mineral formation | T_1446 | In the last several years, many incredible discoveries have been made exploring how minerals behave under high pressure, like rocks experience inside the Earth. If a mineral is placed in a special machine and then squeezed, eventually it may convert into a different mineral. Ice is a classic example of a material that undergoes solid-solid "phase transitions" as pressure and/or temperature is changed. A "phase diagram" is a graph which plots the stability of phases of a compound as a function of pressure and temperature. A phase diagram for water (ice) is included in the Figure 1.6. The phase diagram is split up into 3 main areas for the solid crystalline phase (ice), the liquid phase (water), and the gas phase (water vapor). Notice that increasing pressure lowers the freezing point and raises the boiling point of water. What does that do to the stability conditions of the liquid phase? A sample phase diagram for water. Click image to the left or use the URL below. URL: | text | null |
L_0242 | mineral groups | T_1447 | Minerals are divided into groups based on chemical composition. Most minerals fit into one of eight mineral groups. | text | null |
L_0242 | mineral groups | T_1448 | The roughly 1,000 silicate minerals make up over 90% of Earths crust. Silicates are by far the largest mineral group. Feldspar and quartz are the two most common silicate minerals. Both are extremely common rock-forming minerals. The basic building block for all silicate minerals is the silica tetrahedron, which is illustrated in Figure 1.1. To create the wide variety of silicate minerals, this pyramid-shaped structure is often bound to other elements, such as calcium, iron, and magnesium. Silica tetrahedrons combine together in six different ways to create different types of silicates (Figure 1.2). Tetrahe- drons can stand alone, form connected circles called rings, link into single and double chains, form large flat sheets of pyramids, or join in three dimensions. One silicon atom bonds to four oxygen atoms to form a silica tetrahedron. The different ways that silica tetrahedrons can join together cause these two minerals to look very different. | text | null |
L_0242 | mineral groups | T_1448 | The roughly 1,000 silicate minerals make up over 90% of Earths crust. Silicates are by far the largest mineral group. Feldspar and quartz are the two most common silicate minerals. Both are extremely common rock-forming minerals. The basic building block for all silicate minerals is the silica tetrahedron, which is illustrated in Figure 1.1. To create the wide variety of silicate minerals, this pyramid-shaped structure is often bound to other elements, such as calcium, iron, and magnesium. Silica tetrahedrons combine together in six different ways to create different types of silicates (Figure 1.2). Tetrahe- drons can stand alone, form connected circles called rings, link into single and double chains, form large flat sheets of pyramids, or join in three dimensions. One silicon atom bonds to four oxygen atoms to form a silica tetrahedron. The different ways that silica tetrahedrons can join together cause these two minerals to look very different. | text | null |
L_0242 | mineral groups | T_1449 | Native elements contain atoms of only one type of element. Only a small number of minerals are found in this category. Some of the minerals in this group are rare and valuable. Gold (Figure 1.3), silver, sulfur, and diamond are examples of native elements. | text | null |
L_0242 | mineral groups | T_1450 | The basic carbonate structure is one carbon atom bonded to three oxygen atoms. Carbonates consists of some cation (like C, Fe, Cu, Mg, Ba, Sr, Pb) bonded to a carbonate molecule. Calcite (CaCO3 ) is the most common carbonate mineral (Figure 1.4). Calcite. | text | null |
L_0242 | mineral groups | T_1451 | Halide minerals are salts that form when salt water evaporates. Halite is a halide mineral, but table salt (see Figure bond with various metallic atoms to make halide minerals. All halides are ionic minerals, which means that they are typically soluble in water. Two carbonate minerals: (a) deep blue azurite and (b) opaque green malachite. Azurite and malachite are carbonates that contain copper instead of calcium. Beautiful halite crystal. | text | null |
L_0242 | mineral groups | T_1451 | Halide minerals are salts that form when salt water evaporates. Halite is a halide mineral, but table salt (see Figure bond with various metallic atoms to make halide minerals. All halides are ionic minerals, which means that they are typically soluble in water. Two carbonate minerals: (a) deep blue azurite and (b) opaque green malachite. Azurite and malachite are carbonates that contain copper instead of calcium. Beautiful halite crystal. | text | null |
L_0242 | mineral groups | T_1452 | Oxides contain one or two metal elements combined with oxygen. Many important metal ores are oxides. Hematite (Fe2 O3 ), with two iron atoms to three oxygen atoms, and magnetite (Fe3 O4 ) (Figure 1.7), with three iron atoms to four oxygen atoms, are both iron oxides. Magnetite is one of the most distinctive oxides since it is magnetic. | text | null |
L_0242 | mineral groups | T_1453 | Phosphate minerals are similar in atomic structure to the silicate minerals. In the phosphates, phosphorus bonds to oxygen to form a tetrahedron. As a mineral group they arent particularly common or important rock-forming minerals, but they are important for you and I. Apatite (Figure 1.8) is a phosphate (Ca5 (PO4 )3 (F,OH)) and is one of the major components of human bone! | text | null |
L_0242 | mineral groups | T_1454 | Sulfate minerals contain sulfur atoms bonded to four oxygen atoms, just like silicates and phosphates. Like halides, they form where salt water evaporates. The most common sulfate mineral is probably gypsum (CaSO4 (OH)2 ) (Figure 1.9). Some gigantic 11-meter gypsum crystals have been found (See opening image). That is about as long as a school bus! Gypsum. | text | null |
L_0242 | mineral groups | T_1455 | Sulfides are formed when metallic elements combine with sulfur in the absence of oxygen. Pyrite (Figure 1.10) (FeS2 ) is a common sulfide mineral colloquially known as "fools gold" because it has a golden metallic looking mineral. There are three easy ways to discriminate real gold from fools gold: real gold is extremely dense, real gold does not grow into perfect cubes, as pyrite commonly does, and pyrite smells like rotten eggs (because of the sulfur). Click image to the left or use the URL below. URL: | text | null |
L_0243 | mineral identification | T_1456 | There are a multitude of laboratory and field techniques for identifying minerals. While a mineralogist might use a high-powered microscope to identify some minerals, or even techniques like x-ray diffraction, most are recognizable using physical properties. The most common field techniques put the observer in the shoes of a detective, whose goal it is to determine, by process of elimination, what the mineral in question is. The process of elimination usually includes observing things like color, hardness, smell, solubility in acid, streak, striations and/or cleavage. Check out the mineral in the opening image. What is the minerals color? What is its shape? Are the individual crystals shiny or dull? Are there lines (striations) running across the minerals? In this concept, the properties used to identify minerals are described in more detail. | text | null |
L_0243 | mineral identification | T_1458 | Color may be the first feature you notice about a mineral, but color is not often important for mineral identification. For example, quartz can be colorless, purple (amethyst), or a variety of other colors depending on chemical impurities Figure 1.1. | text | null |
L_0243 | mineral identification | T_1459 | Streak is the color of a minerals powder, which often is not the same color as the mineral itself. Many minerals, such as the quartz in the Figure 1.1, do not have streak. Hematite is an example of a mineral that displays a certain color in hand sample (typically black to steel gray, sometimes reddish), and a different streak color (red/brown). | text | null |
L_0243 | mineral identification | T_1460 | Luster describes the reflection of light off a minerals surface. Mineralogists have special terms to describe luster. One simple way to classify luster is based on whether the mineral is metallic or non-metallic. Minerals that are opaque and shiny, such as pyrite, have a metallic luster. Minerals such as quartz have a non-metallic luster. Different types of non-metallic luster are described in Table 1.1. Luster Adamantine Earthy Pearly Resinous Silky Vitreous Appearance Sparkly Dull, clay-like Pearl-like Like resins, such as tree sap Soft-looking with long fibers Glassy The streak of hematite across an unglazed porcelain plate is red-brown. | text | null |
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