Download Layers of The Earth

Layers of The Earth
What are the 3 main layers
of Earth? How do they differ
in thickness and
composition?
What are two types of crust
and how do they differ?
What is the lithosphere and
the asthenosphere?
The Earth has several distinct layers:
The crust – the outermost layer of the Earth, comprised of 2
types of crust - continental and oceanic. The crust has a
variable thickness, being 35-70 km thick in the continents and
5-10 km thick in the ocean basins. Continental crust has a
varying thickness, being thickest at mountain chains, and a
relatively light density compared to the materials of the other
layers. Its base is granite, whereas the base of oceanic crust
is basalt, which is denser than granite.
The mantle – the thickest layer, is about 2900 km thick, and
is separated into the upper and lower mantle. This is where
most of the internal heat of the Earth is located. Large
convective currents in the mantle circulate heat and may drive
plate tectonic processes. The upper mantle and the crust is
called the lithosphere and is solid. Below this the mantle has a
layer called the asthenosphere which is putty-like in nature
and on which the tectonic plates move.
- Mohorovicic discontinuity - the boundary between the crust
and upper mantle where earthquake waves speed up.
How does the inner and
outer core differ?
What connection do
scientists infer between the
outer core and Earth’s
magnetic field?
- Gutenburg discontinuity - the boundary between the mantle
and the outer core where P-waves change velocity and Swaves disappear (are stopped). P - waves and S- waves are
the 2 types of seismic (earthquake) body waves.
The core - is separated into the liquid outer core and the solid
inner core. The outer core is 2300 km thick and the inner core
is 1200 km thick. The outer core is composed mainly of a
nickel-iron alloy, while the inner core is almost entirely
composed of iron. Belief that the outer core is liquid is due to
the cessation of S-waves, creating a shadow zone. Also, if the
outer core is liquid, as inferred, the spinning movement this
liquid iron could form a type of electrical current and be
responsible for Earth's magnetic field. The inner core is
believed to be solid due to the pressure from the other layers
upon it.
Summaries