new oceanic crust is being created at mid-ocean ridges on earth.
where is new oceanic crust being created on earth?
at mid-ocean ridges
oceanic crust, which forms the bedrock of abyssal plains, is continuously being created at mid-ocean ridges (a type of divergent boundary) by a process known as decompression melting. plume-related decompression melting of solid mantle is responsible for creating ocean islands like the hawaiian islands, as well as the ocean crust at mid-ocean ridges. this phenomenon is also the most common explanation for flood basalts and oceanic plateaus (two types of large igneous provinces). decompression melting occurs when the upper mantle is partially melted into magma as it moves upwards under mid-ocean ridges. this upwelling magma then cools and solidifies by conduction and convection of heat to form new oceanic crust. accretion occurs as mantle is added to the growing edges of a tectonic plate, usually associated with seafloor spreading. the age of oceanic crust is therefore a function of distance from the mid-ocean ridge. the youngest oceanic crust is at the mid-ocean ridges, and it becomes progressively older, cooler and denser as it migrates outwards from the mid-ocean ridges as part of the process called mantle convection.
abyssal plain
new oceanic crust, closest to the mid-oceanic ridges, is mostly basalt at shallow levels and has a rugged topography. the roughness of this topography is a function of the rate at which the mid-ocean ridge is spreading (the spreading rate). magnitudes of spreading rates vary quite significantly. typical values for fast-spreading ridges are greater than 100 mm/yr, while slow-spreading ridges are typically less than 20 mm/yr. studies have shown that the slower the spreading rate, the rougher the new oceanic crust will be, and vice versa. it is thought this phenomenon is due to faulting at the mid-ocean ridge when the new oceanic crust was formed. these faults pervading the oceanic crust, along with their bounding abyssal hills, are the most common tectonic and topographic features on the surface of the earth. the process of seafloor spreading helps to explain the concept of continental drift in the theory of plate tectonics.
abyssal plain