Download Name Date_________Core____ Inside the Restless Earth – Ch. 4

Name ________________
Date_________Core____
Inside the Restless Earth – Ch. 4 Plate Tectonics
Study Guide - ANSWERS
Record key notes for each listed component.
Section 1 – Inside the Earth
A. **The Composition of the Earth**
1. Crust
Outermost layer; ranging from 5-100 km thick; thinnest layer; layer we
live on; part of the lithosphere; less than 1% of Earth’s mass; granite & basalt
a. Continental crust
Composition similar to granite; thick; less dense; average 30 km thick;
makes up continents we see
b. Oceanic crust
Composition similar to basalt; thin; more dense; generally 5-8 km thick;
under the water
2. Mantle
Between the crust and core (2nd layer from top); extremely thick; most of
Earth’s mass; too far down to drill; composition of silica (sand) & olivine;
underwater volcanoes are windows to the mantle
3. Core
Densest layer; maybe made mostly of iron and then nickel; center of the Earth from mantle;
Mars fits within our core; 33% of Earth’s mass; 6,856 km in diameter
B. The Structure of the Earth
1. **Lithosphere**
“rock sphere;” rigid layer, made up of crust and upper rigid part of the mantle;
divided into pieces called tectonic plates; outer layer
2. **Asthenosphere**
“weak sphere;” soft layer; putty like; lithosphere (tectonic plates) flows on this
3. Mesosphere
“middle sphere;” strong; lower part of the mantle (which includes
Asthenosphere) to the outer core
4. Outer core
Liquid layer; lies beneath the mantle and surrounds the inner core; 2,200 km
thick
5. Inner core
Solid; dense center; 6,378 km below surface, 1, 228 km thick
C. Tectonic Plates
1. What are they?
Tectonic plates are pieces of the lithosphere that move around on top of the
asthenosphere.
2. **What two things occur often at these plate boundaries?**
Earthquakes and volcanoes
D. Mapping the Earth’s Interior - **How do we know more about inside the Earth? Explain.**
When earthquakes occur, vibrations called seismic waves travel through the Earth.
Seismic waves travel at different speeds depending on the density and strength of
the material.
Section 2 – Restless Continents
A. Wegener’s Theory
1. **continental drift**
a theory that continents can drift apart from one another and have done so in
the past
a. Proposed by __Alfred Wegener___
2. Evidence supporting the theory
a. Continents fit together like a puzzle
b. Same fossils of plants and animal species are found on different continents
c. Evidence left by ancient glaciers
d. Climatic conditions or similar mountains found on different continents
3. **Theory not accepted because… What was the big question not answered?**
What force of nature could move entire continents?
B. The Break-up of **Pangaea**
Pangaea is Greek for “all earth”; Pangaea is a single landmass of all the continents
joined together (Wegener included this in his theory); can date back to 245 million
years ago
C. **Sea-floor Spreading**
Sea-floor spreading is the process by which new oceanic lithosphere is created as
older materials are pulled away. This occurs at mid-ocean ridges. This was the
last evidence Wegener needed. Discovered by Harry Hess.
Newer crust/rock is found along the Mid-Atlantic Ridge, while the oldest crust can be
found closer to the continents
Section 3 – Theory of Plate Tectonics – **Explain plate tectonics.**
Plate tectonics is a theory that the Earth’s lithosphere is divided into tectonic
plates that move around on top of the asthenosphere.
Plates move about 2 cm per year
A. **Tectonic Plate Boundaries**
1. Convergent
When two tectonic plates push/crash/collide into one another; mountains
can be formed
a. Continental/oceanic
When a tectonic plate with oceanic crust and tectonic plate with
continental crust collide; Andes Mountains in S. America
b. Oceanic/oceanic
When tectonic plate with oceanic crust and tectonic plate with
oceanic crust collide; occur under water; Mariana Trench
c. **Continental/continental**
When tectonic plate with continental crust and tectonic plate with
continental crust collide; Himalayan Mountains
2. Divergent
When tectonic plates move away from one another;
Mid-ocean ridges/mid-Atlantic ridge; Great Rift Valley in Africa; Iceland splitting
3. Transform
When tectonic plates slide past each other horizontally; San Andreas Fault
Section 4 – Deforming the Earth’s Crust
A. **Types of Stress – What is stress?**
Amount of force per unit area that is put on a given material
1. Compression – Define and identify what plate boundary it involves.
Type of stress that occurs when an object is squeezed; think of
spaghetti noodle; convergent boundaries
2. Tension – Define and identify what plate boundary it involves.
Type of stress that occurs when forces act to stretch or pull apart an object; think
of rubber-band; divergent boundary
Define and draw pictures/diagram for folding and faulting.
B. **Folding**
Rock layers bend
*compression = syncline and anticline; tension/shear = monocline
1. Anticline
Rock layers bend upward
2. Syncline
Rock layers bend downward
3. Monocline
Rock layers bend to where both ends are still horizontal
C. **Faulting**
Rock layers break
*compression = reverse fault; tension = normal fault; shear = strike-slip fault
1. Normal
Rock layers break and hanging wall moves down relative to footwall;
think of sliding down a slide
2. Reverse
Rock layers break and hanging wall moves up relative to footwall;
think of sliding up a slide (not normal)
3. Strike-slip
Opposing forces cause rock to break and move horizontally; occurs at
San Andreas Fault in California
D. Mountain building
1. Folded mountain
Form when rock layers are squeezed (compressed) together and
pushed upward
2. Fault block mountain
Form when faulting causes large blocks of the Earth’s crust to drop
down relative to other blocks
3. Volcanic mountain
Form when molten rock erupts onto the Earth’s surface