1. PLATE TECTONICS Chapter 7 – Inside the Restless Earth

2. Section 1 – Inside the Earth
The Earth is made of 3 layers with based on what
each layer is made of (COMPOSITION):
Crust – the outermost layer of the Earth. Ranges from 5 to 100 km thick. (The thinnest layer) Less than 1% of the Earth’s mass.
* Continental crust – composition similar to granite. Average thickness is 30 km.
* Oceanic crust – composition similar to basalt. It is generally between 5 and 8 km thick.

3. Mantle – the layer of the Earth between the crust and the core
Mantle – the layer of the Earth between the crust and the core. Extremely thick and contains most of the Earth’s mass. Approximately 2,900 km thick.
3. Core – extends from the bottom of the mantle to the center of the Earth. Approximately 33% of the Earth’s mass. Made mostly of iron with small amounts of nickel and some sulfur and oxygen.

5. The Earth is divided into 5 based on their
physical properties (MECHANICAL):
Lithosphere – the outermost, rigid layer of the Earth. Made of the crust and the rigid upper part of the mantle. Divided into tectonic plates.
Asthenosphere – the soft layer of the mantle on which pieces of the lithosphere move. Made of solid rock that flows very slowly.
Mesosphere – strong, lower part of the mantle. Extends down to the core.

6. Outer Core – the liquid layer of the Earth’s core that lies beneath the mantle and surrounds the inner core.
Inner Core – The solid, dense center of our planet. Extends to the center of the Earth, about 6,378 km beneath the surface.

9. These layers can be described by what they are made of (COMPOSITION) and how the act (PHYSICAL): Composition: Physical: Granite Rigid Basalt Strong Iron Liquid Nickel Solid Sulfur Soft Oxygen

10. Tectonic plates are pieces of the lithosphere
that move around on top of the asthenosphere.
Tectonic plates are different sizes and may
contain oceanic crust, continental crust or a
combination of both. Each piece fits together
like a giant jigsaw puzzle.
Plate boundaries are areas where plates come
into contact with each other.

12. Section 2 – Restless Continents
Continental Drift is the theory that continents
can drift apart from one another and have done
so in the past. This was first described by Alfred
Wegener in the early 1900’s.
This theory explained why fossils of
the same plant and animal species
are found on both side of the Atlantic
Ocean. It also explained why some
of the continents seemed to fit together
like a jigsaw puzzle.

15. Plates move because of the convection currents in the mantle.

16. Mid-Ocean ridges are
underwater mountain chains.
Along these mountains, you will
find sea-floor spreading.
During this process new oceanic
lithosphere is created as magma
rises toward the surface.

17. Section 3 – The Theory of Plate Tectonics
Plate tectonics is the theory that the Earth’s
lithosphere is divided into tectonic plates that
move around on top of the asthenosphere.
A boundary is a place where tectonic plates
touch.
There are 3 types of boundaries and they are
labeled by how the boundaries meet.

18. Convergent Boundaries – two tectonic plates collide
Convergent Boundaries – two tectonic plates collide. (Usually creates mountains.)
Divergent Boundaries – two tectonic plates separate. (New sea-floor is created.)
3. Transform Boundaries – two tectonic plates slide past each other horizontally. ( An example is the San Andreas Fault.)

21. At convergent boundaries,
subduction zones are
created when one plate
subducts (or goes
underneath) another plate.
These create ocean
trenches, volcanoes and
earthquakes.

23. Scientists use satellites and global
positioning to track the movement of the
Earth’s plates. Tectonic movement is so
slow it is measured in centimeters per year.

24. Section 4 – Deforming the Earth’s Crust
Stress is the amount of force per unit area
on a given object. Stress applied to rock will
cause it to change.
Deformation – process by which the shape
of a rock changes because of stress. Rocks
reach their elastic limit and break.

25. Compression – type of stress that occurs when an object is squeezed
Compression – type of stress that occurs when an object is squeezed. (Two tectonic plates colliding.
Tension – stress that occurs when forces act to stretch an object. (Divergent boundaries.)

26. Folding is the bending of rock layers
because of the stress in the Earth’s crust.
Scientists assume that all rock layers started out
as horizontal layers. The folds in rock layers
shows that deformation has taken place.
There are 2 most common types of folding;
synclines and anticlines.

27. Anticlines – upward-arching folds in rock.
Synclines – down-ward, troughlike folds in rock.

28. The surface along which
rocks break and slide past
each other is called a fault.
The foot wall is sitting down
and the hanging wall is
“hanging” or resting on the
foot wall.

29. Normal fault – the hanging wall moves down relative to the footwall.
Reverse fault – the hanging wall moves up relative to the footwall.
3. Strike-slip fault – opposing forces cause rock

30. The movement of tectonic
plates can create mountains.
Folded mountains – form when rock layers are squeezed together and pushed upward.
Fault-Block Mountains – form when tension causes large blocks of the Earth’s crust to drop down relative to other blocks.

31. 3. Volcanic mountains – magma that rises to the surface, cools and forms mountains. May be on the surface or under the water.

32. There are 2 types of
vertical movement of the
Earth’s crust; uplift and
subsidence.
Uplift – the rising of
regions or Earth’s crust to
higher elevations.
Subsidence – the sinking
of regions of Earth’s crust
to lower elevations.

33. Subsidence can also occur when the
lithosphere becomes stretched in rift zones.
A rift zone is a set of deep cracks that forms
when 2 tectonic plates are pulled away
from each other.