Page 77 - Science Course 2 (Book 2)
P. 77
Mo10-L1b: What is the Structure of the Geosphere?
Ancient Earth was much hotter than it is today and The crust is the thin outer layer of the geosphere.
thermal energy melted some of the rock.
Oceanic crust is made of the dense igneous rocks
basalt and gabbro.
Gravity pulled denser materials through the melted
rock toward Earth’s center, forming layers.
Ocean Crust Continental Crust
(more dense) (less dense)
Continental crust, which is thicker but less dense
than oceanic crust, is made of igneous, metamor-
phic, and sedimentary rock.
The mantle is the thick, rocky middle layer of the
geosphere.
Key Concept The mantle has the largest volume of any layer of
Earth, and much of it is made of the rock peridotite.
What is the Structure of the Geosphere?
Why is the geosphere layered?
Mantle
Crust
The crust and the uppermost mantle form a brittle
outer layer called the lithosphere.
The weak, partially melted layer of the mantle is
called the asthenosphere.
lithosphere
asthenosphere
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