2. Crust:
• t is the outermost solid shell of a rocky planet
or natural satellite, which is chemically distinct
from the underlying mantle. The crusts
of Earth, the Moon, Mercury, Venus, Mars, Io,
and other planetary bodies have been
generated largely by igneous processes, and
these crusts are richer in incompatible
elements than their respective mantles.
3. Crust and mantle:
• The crust of the Earth is composed of a great
variety
of igneous, metamorphic, and sedimentary ro
cks. The crust is underlain by the mantle. The
upper part of the mantle is composed mostly
of peridotite, a rock denser than rocks
common in the overlying crust. The boundary
between the crust and mantle is
conventionally placed at the Mohorovičić
discontinuity, a boundary defined by a
contrast in seismic velocity.
4.
5. Composition:
• The continental crust has an average
composition similar to that
of andesite. Continental crust is enriched
in incompatible elements compared to
the basaltic ocean crust and much enriched
compared to the underlying mantle.
6.
7. Mantle:
• The mantle is a part of a terrestrial planet or
other rocky body large enough to
have differentiation by density. The interior
of Earth, similar to the other terrestrial
planets, is chemically divided into layers. The
mantle is a layer between the crust and
the outer core. Earth's mantle is a silicate
rocky shell about 2,900 kilometers (1,800 mi)
thick that constitutes about 84% of Earth's
volume.
8.
9. Structure:
• The mantle is divided into sections which are
based upon results from seismology. These layers
(and their thicknesses/depths) are the following:
the upper mantle (starting at the Moho, or base
of the crust around 7 to 35 km (4.3 to 21.7 mi)
downward to 410 km (250 mi)), the transition
zone (410–660 km or 250–410 mi), the lower
mantle (660–2,891 km or 410–1,796 mi), and
anomalous core–mantle boundary with a variable
thickness (on average ~200 km (120 mi) thick).
10. Characteristics:
• The mantle differs substantially from the crust
in its mechanical properties which is the direct
consequence of chemical composition change
(expressed as different mineralogy). The
distinction between crust and mantle is based
on chemistry, rock
types, rheology and seismic characteristics.
The crust is a solidification product of mantle
derived melts, expressed as various degrees of
partial melting products during geologic time.
11.
12. Temperature:
• In the mantle, temperatures range between
500 to 900 °C (932 to 1,652 °F) at the upper
boundary with the crust; to over 4,000 °C
(7,230 °F) at the boundary with the core.
Although the higher temperatures far exceed
the melting points of the mantle rocks at the
surface (about 1200 °C for
representative peridotite), the mantle is
almost exclusively solid.
