Section 1: Inside the Earth
Earth's layers
1. Crust- less than 1% of earth's mass
- 5 to 100 km thick and thin and solid layer above the mantle
Types of crust:
1. oceanic- thinner but denser than continental because it contains twice as much as Fe, Ca, and
Mg
2. continental crust- thicker but less dense than oceanic crust
2. Mantle- layer between the crust and core and contains most of Earth's
mass (67%)
-denser
than crust because it contains more
Magnesium
How do scientists know about the composition of mantle? -from magma that flows out of active
volcanoes on ocean floor
5 Physical Layers of the Earth
1. Lithosphere- outermost, rigid layer
-made of crust and upper part of mantle and divided into tectonic plates
2. Asthenosphere- plastic layer of mantle
-where tectonic plates move and made of solid rock flowing very slowly
3. Mesosphere- lower part of mantle
-extends from bottom of asthenosphere to the core
4. Outer Core- liquid layer and 2,200 km thick
5. Inner core- solid dense center and 1,230 km thick
- core is made mainly of Iron (Fe) and nickel (Ni)
Tectonic Plates- block of lithosphere made up of the crust and outermost part of the mantle
How do scientists know about deepest parts of the Earth? They
study seismic waves caused by earthquakes.
-Seismic waves travel at different speeds
depending on density
Seismograph- used to measure the density of
Earth’s layers
Check Points:
1. Identify the layers of the earth by their composition
2. Identify the layers of the Earth by their physical properties.
Section 2: Continental Drift
Alfred Wegener- wrote about Continental Drift
Continental Drift- continents once formed a single landmass, broke up and drifted to present day
locations
-explained why fossils of same plant and animals are found on different sides of Atlantic Ocean
Pangaea- Greek for "all earth"; single huge continent 245 million years ago
- split into two huge continents Laurasia and Gondwana
Sea- Floor Spreading- process by which new oceanic crust forms as
magma rises toward the surface and solidifies
Magnetic reversals- happen when Earth’s magnetic poles
change places
-used as evidence for sea-floor spreading
Mid-ocean ridges- places where sea-floor spreading takes place
GPS (Global Positioning System) - used to measure
movement of tectonic plates
Check Point:
In your own words, define continental drift and sea-floor spreading
Section 3: Plate tectonics Theory
Plate tectonics- explains how tectonic plates move and change
shape
Boundary- where two tectonic plates meet
3 Types of boundaries
1. Convergent boundary- formed when two tectonic plates collide
2. Divergent boundary- when two tectonic plates move away from each other
3. Transform boundary- when two tectonic plates slide past each other
3 possible causes of Plate tectonics
1. Ridge Push- happens at mid-ocean ridge and oceanic crust slides downhill
2. Convection- hot rock within earth rises, cooler rock sinks
3. Slab Pull- when denser oceanic crust sinks, it pulls the rest of the tectonic plate with it
Section 4: Earth's Deformation
1. Deformation- happens when the shape of a rock changes due to stress
2. Compression- when two tectonic plates collide at convergent boundary; forms mountains
- stress that squeezes rock layers
3. Tension- when tectonic plates move away from each other
- stress that stretches rock layers
-occurs at divergent boundaries and forms at mid-ocean ridges
Folding- bending of rock layers due to stress
Fault- break in a rock along which one block slides relative to another
Types of fault
1. Normal Fault- happens during tension when tectonic plates pull apart
- hanging wall moves down, footwall moves up
2. Reverse fault- happens during compression when tectonic plates push rock together
- hanging wall moves up, footwall moves down
3. Strike-slip fault- happens along transform boundary
-when rocks break and move horizontally
Types of mountains
1. Folded Mountain- highest mountain ranges in the world and forms when rocks are pushed
together
2. Fault- Block Mountain- has sharp, jagged peaks and forms during tension(rock layers
stretches)
3. Volcanic Mountain - forms at convergent boundaries along subduction zones
- formed by magma that reaches earth’s surface
Ring of Fire- where most active volcanoes are found
Uplift- rising of parts of Earth's crust to higher elevations
Subsidence- sinking of earth's crust
Rift Zone- deep cracks that form between tectonic plates pulling away from each other
Check Points
1. How do rift zones form?
2. What are the three types of faults?