Earth Science Unit 3

What are the compositional layers

crust (continental and oceanic), mantle, and core (inner and outer)

What are the functional layers

lithosphere (crust and upper mantle) and asthenosphere (lower mantle/rest of the mantle)

Ps 104:8: “The mountains rose; the valleys sank. The water went to the places you made for it.”

Chapter 4

Explain the continental drift hypothesis

First proposed by Alfred Wegener; supercontinent called Pangaea began breaking apart about 200 million years ago; continents “drifted” to present positions and “broke” through the ocean crust

What evidence did Wegener use? Why was it abandoned?

Evidence: fit of South America/Africa, fossils match across the seas, rock types and mountain ranges match, glacial evidence

It was abandoned because there was no mechanism to explain it (could see the plate tectonics were attached)

Explain plate tectonics

A theory that stemmed from Wegener’s theories; states that the earth is divided into geologic plates that are moving relative to each other

Pieces of lithosphere

Geologic plates

What is the lithosphere?

The crust and upper mantle; more rigid/solid, so it breaks more easily

What is the athenosphere?

The lower part of the mantle, exists beneath the lithosphere, hotter and weaker than the lithosphere, which means it can move (allows for movement of the lithosphere above it)

The plate boundary where plates are actually moving (western coast of North/South America)

active margins

Plate boundary where no movement or tectonic activity is occurring (eastern coast of North/South America)

passive margins

What is the surface evidence for plate tectonics (in addition to continental drift)?

• earthquake distribution

• volcano distribution

• mountain range distribution

• oceanic ridge distribution

• oceanic trench distribution

Plates move away from each other; 1 plate splits apart into 2 plates; new lithosphere is created; can be oceanic or continental

Divergent plate boundaries

Plates move toward each other; 2 plates collide with each other; lithosphere is destroyed; 3 types based on the type of lithosphere

Convergent plate boundaries

Plates move horizontal past each other; 2 plates move horizontally; nothing created or destroyed

Transform plate boundaries

Explain the two different types of divergent boundaries

1. Oceanic Divergent Boundaries: (seafloor spreading), magma pushing up with immense pressure that it pushes the ocean floor up into a ridge and rips it open (Mid-Atlantic Ridge)

2. Continental Divergent Boundaries: (continental rifts), magma pushes up forcing lithosphere to rip apart which creates a rift; however, no ridge is formed here because the continental crust (or lithosphere) is too thick and not as dense (East African Rift)

Explain the three different types of convergent plate boundaries, and what are examples of each?

1. Ocean-continent: oceanic and continental lithosphere collide (Andes Mountains/Cascade Mountains)

2. Ocean-ocean: oceanic and oceanic lithosphere collide (Japan)

3. Continent-continent: continental and continental lithosphere collide (Himalayan Mountains)

the cause for ocean-continent and ocean-ocean convergent boundaries; oceanic lithosphere sinks into the athenosphere

Subduction

A weak spot in the middle of a plate where magma comes up; what are the two types?

Hot spots; Oceanic (Hawaii) and Continental (Yellowstone)