Earthstructureinternal - mantle - Copy.ppt

Earth's mantle

1. Geochemistry
Lecture
Geochemistry

2. Structure of the Earth
2
The stratification of
Earth into distinct
layers represents a
pivotal event in its
geologic history. This
process culminated in
the development of a
core, a crust, and
subsequently, the
formation of
continents. During this
differentiation, lighter
elements were
expelled from the
interior, leading to the
creation of the ocean
and atmosphere. The
four segments are of
equal dimensions.

3. Structure of the Earth
3
Mantle
The Earth's mantle is the thick, solid
layer located between the crust and the
core, playing a crucial role in the planet's
geodynamics and thermal evolution. It
extends from the base of the crust (the
Mohorovičić discontinuity, or Moho)
down to the core-mantle boundary,
encompassing approximately 84% of
Earth's volume.

4. Structure of the Earth
4
Mantle
1.Composition:
•Mineralogy: The mantle is primarily composed of silicate
minerals rich in magnesium and iron, such as olivine, pyroxenes,
and garnet.
•Chemical Composition: Dominated by elements such as oxygen,
silicon, magnesium, iron, aluminum, and calcium. The upper
mantle is often distinguished by a higher concentration of olivine
and pyroxene, whereas the lower mantle has minerals like
bridgmanite and ferropericlase.

5. Structure of the Earth
5
Mantle
2. Structure:
•Upper Mantle: Extends from the Moho to a depth of about 660
kilometers. It includes the lithosphere (rigid uppermost part) and the
asthenosphere (a partially molten, ductile region that allows for plate
motion).
•Transition Zone: Lies between 410 and 660 kilometers, characterized by
changes in mineral structures due to increasing pressure.
•Lower Mantle: Extends from 660 kilometers to the core-mantle
boundary at about 2,900 kilometers. It is more homogeneous in
composition and exhibits a more rigid behavior compared to the upper
mantle.

6. Structure of the Earth
6
Mantle
3. Physical Properties:
•Temperature and Pressure: Both increase with depth. Temperatures range
from about 500°C near the Moho to over 4,000°C at the core-mantle
boundary. Pressure increases from around 0.2 GPa at the Moho to
approximately 140 GPa at the base of the mantle.
•Viscosity: Varies significantly, being lower in the asthenosphere (allowing
for convection) and higher in the deeper parts of the mantle.

7. Structure of the Earth
7
Mantle
4. Dynamics:
•Mantle Convection: The mantle undergoes slow, convective
movements driven by heat from the core and radioactive decay
within the mantle. This convective motion is responsible for the
movement of tectonic plates on the Earth's surface.
•Plumes and Hotspots: Mantle plumes, rising columns of hot,
solid material, can create volcanic hotspots, leading to the
formation of volcanic islands and continental rift zones.

8. Structure of the Earth
8
Mantle
5. Role in Earth's Systems:
•Tectonic Activity: The mantle's convective currents drive plate tectonics,
influencing the creation and destruction of crust, mountain building,
earthquakes, and volcanism.
•Heat Transfer: Acts as a major conduit for transferring heat from the
Earth's interior to the surface, playing a critical role in the thermal evolution
of the planet.
In summary, the Earth's mantle is a dynamic and integral part of the
planet's internal structure, influencing geological and geophysical
processes that shape the Earth's surface and its long-term evolution.