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Surface map of oceanic crust showing the generation of younger (red) crust and eventual destruction of older (blue) crust. This demonstrates the crustal spatial evolution at the Earth's surface dictated by plate tectonics. Earth's crustal evolution involves the formation, destruction and renewal of the rocky outer shell at that planet's surface.
The internal structure of Earth. In geology, the crust is the outermost solid shell of a planet, dwarf planet, or natural satellite.It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be defined based on its phase (solid crust vs. liquid mantle).
Mohorovičić discontinuity – Boundary between the Earth's crust and the mantle; Mountain – Large natural elevation of the Earth's surface; Mid-ocean ridge, also known as Oceanic ridge – Basaltic underwater mountain system formed by plate tectonic spreading; Oceanic trench – Long and narrow depressions of the sea floor
Continental crust is a tertiary crust, formed at subduction zones through recycling of subducted secondary (oceanic) crust. [17] The average age of Earth's current continental crust has been estimated to be about 2.0 billion years. [20] Most crustal rocks formed before 2.5 billion years ago are located in cratons.
Earth systems across mountain belts include the asthenosphere (ductile region of the upper mantle), lithosphere (crust and uppermost upper mantle), surface, atmosphere, hydrosphere, cryosphere, and biosphere. Across mountain belts these Earth systems each have their own processes which interact within the system they belong.
Crustal thickening has an upward component of motion and often occurs when continental crust is thrust onto continental crust. Basically nappes (thrust sheets) from each plate collide and begin to stack one on top of the other; evidence of this process can be seen in preserved ophiolitic nappes (preserved in the Himalayas) and in rocks with an inverted metamorphic gradient.
A tectonic evolution diagram from 2.45 Ga to 1.95 Ga, proposed by Zhao et al. [4] (1) At around 2.45 Ga, the oceanic crust of Ordos Block was subducted beneath Yinshan Block, making igneous rocks. (2) Sedimentary rocks deposited in Ordos Block between 2.0-1.95 Ga. (3) Both continents of Yinshan Block and Ordos Block met at around 1.95 Ga and an ...
The importance of this geological setting lies in the ability to study and obtain a better understanding of geologic history. Using information from this area has provided direct geologic evidence on the nature and evolution of the Earth before 3.0 Ga. Evidence of early crust, ocean chemistry, biota and atmosphere can be derived from the BGB. [3]