as a whole. In some cases, faulted blocks have shifted more than 50 miles from the apex of the dome. Along detachment surfaces, mylonite forms due to shear. The Ruby Mountains-East Humboldt, close to Elko, and the Northern Snake Range, close to Utah, are the two most researched core complexes. At the time of the Pleistocene glaciations, Nevada experienced temperatures up to 15 degrees Fahrenheit lower, eight inches more of annual rainfall and lower evaporation. Although it was drier overall than many neighboring areas, glaciers did form in the Ruby Mountains and East Humboldt Range. Small areas of eastern Nevada in the White Pine, Grant Ranges, Snake and Schell Creek mountains were also glaciated, along with the Toquima, Toiyabe and Monitor Ranges in the center of the state. Geologists debate whether the 11,918 foot tall Charleston Peak was glaciated as well. Dozens of large lakes filled the valleys in the region, accumulating fine silt and developing alkaline chemical conditions that precipitated tufa calcium carbonate mounds. Lake Lahontan in the northwest was the largest lake overall and flooded up to 8600 square miles 14,000 years ago. The lake grew in three different phases, with volcanic ash and silt at its bottom. Today, Pyramid Lake is a remnant of Lahontan, where it was once over 900 feet deep. Elsewhere, Clover, Franklin and Waring lakes developed near the Ruby Mountains. Lake Railroad occupied Railroad Valley, while Lake Toiyabe and Lake Desatoya formed in Big Smoky Valley and Smith Creek Valley respectively. Natural resource geology Mining and mineral resources have played an important role in the state's past and present economy. Named the Silver State for silver deposits which spurred early settlement and statehood in the 1800s, Nevada is today the leading producer of gold in the US, mining five million ounces annually. In 2012, $10.5 billion of materials were mined, directly employing over 15,000 people. Gold-bearing skarn in the Battle Mountain region of northeast Nevada is an important target for mining. Up to 263 polymetallic veins contain sphalerite, galena, jamesonite and tetrahedrite. Polymetallic molybdenum, antimony, uranium, copper, gold zinc, lead and silver ores have been mined in the Reese River area since the 1800s. In 1961, Carlin-type gold deposits were discovered near Carlin, Nevada. Paleozoic limestone, formed at the ancient continental margin, contains nearly microscopic gold associated with pyrite and arsenic sulfides and particularly jasperoid in folds and faults. Over 200 million ounces