Download Earth Science 6th grade

Forces Shaping Earth
Earth’s Moving Plates
Uplift of Earth’s Crust
Earth’s Moving Plates
A. Geologists use earthquakes and
surface rocks to indirectly
observe Earth’s interior.
1. Seismic waves change speed and
direction depending on the density and
material they travel through.
2. Forces bring rocks formed deep
within Earth to the surface.
3. Evidence suggests that the Earth
is formed of different materials in
layers.
B. Earth has four main layers.
1. Inner core – dense iron core; very
hot and dense; solid iron center
2. Outer core – molten metal above
inner core.
3. Solid layer that flows slowly like putty
is the mantle. The mantle is the
largest layer.
4. Outermost layer is the crust.
The crust is made of Tectonic plate.
C. Earth’s structure – theories based on
physical properties of density,
temperature, and pressure that
change with depth.
D. Earth’s moving plates are sections
of the lithosphere, the rigid upper
part of the mantle and crust.
E. Plate boundaries are the edges
where plates meet.
1. Tension can pull plates apart, resulting
in new lithosphere forming in the gaps.
2. Colliding plates could cause mountains
to form as rock crumbles and folds.
3. Subduction occurs when a denser plate
sinks underneath a less dense plate.
4. Shearing, or sliding causes faults
and earthquakes as two plates slide
past each other.
F. Plate movement theory –
convection in the mantle circulates
material and moves plates.
1. Ridge-push at mid-ocean ridges
causes plates to slide down the slope.
– pull happens as plates
move away from mid-ocean
ridges and become denser.
2. Slab
Section 2
Uplift of Earth’s Crust
A. Mountains form in different ways.
1. Fault-block mountains- form from huge
tilted blocks of rock separated from
surrounding rock by large faults.
2. Folded mountains- formed by
compressed forces folding rock layers.
3. Upward mountains- forces push up
Earth’s crust and allow the sedimentary
rock to erode, leaving igneous or
metamorphic rock.
4. Over time, layers of lava can form a coneshaped volcanic mountain.
5. Hot spots formed by plumes of magma in
the mantle can cause under water volcanic
mountains.
B. Isostacy principle indicates Earth’s crust
and lithosphere float on the upper mantle.
1. Earth’s crust is thicker under
mountains.
2. When mountains erode, the crust rises
because the weight has been removed.