It won’t have the guts to do that again!

C. Earth’s Interior

1.At Earth’s center is the inner core made of iron and nickel in a solid state. Inner Core

2. The outer core is made of iron and nickel that is in a liquid state. Outer Core

3. Surrounding the cores is the mantle made of compounds rich in iron, silicon, and magnesium. Mantle

4. The crust is a thin, rigid layer that includes Earth’s surface. Crust

a. The lithosphere floats upon the asthenosphere. b. The asthenosphere is a slushy layer of the mantle.

Pangaea

Refer to page 79 in Oceanography Book or page 24 & 31 in the old Marine Bio Book (red)

CHAPTER 2 PLATE TECTONICS “Shaking the Earth”

I. What is Plate Tectonics? A. Early Ideas About Plate Movements 1. In 1500’s explorers noticed similarities between eastern coast of South America and western coast of Africa. South America Africa

This reptile, Mesosaurus, was found in freshwaters of Pangaea 260 million years ago in what is now Africa and South America. 2. Similar fossils were found on these two continents.

Distribution of fossils across continents that are separated today.

3. Alfred Wegener first proposed that the continents moved on fluid layers, but had no evidence to support this theory. B. The Theory of Plate Tectonics 1. Continents are embedded in lithospheric plates that move, carrying the continents with them. 2. The theory explains why earthquakes and volcanoes occur at certain locations and how new crust forms along the ocean floor. 3. Locations of Earthquakes and Volcanoes a. Occur not at random, but at specific sites. b. These are areas where plates come together.

Events related to crustal plates

4. Magnetism and the Age of the Ocean Floor Formation of Seafloor at the Midocean Ridge a. Seafloor spreading occurs at midocean ridges b. Magnetic reversals in Earth’s magnetic field are evidence for this.

Continental- many rocks (silica based) Oceanic- mostly Basaltic (samples taken by Glomar challenger)

Reconstruction of former plate motions. Based on magnetic anomaly-patterns in the oceans it is possible to reconstruct the face of the earth back in time for the period we have oceanic lithospere preserved We can see that the oldest ocean floor is ca ≈180Ma, how Can we reconstruct plate-motions before mid-Jurassic time?

Absolute movements of Earth’s crust by GPS

Earth’s Magnetic Field Shows Periodic Reversals

Oceanic Crust is Pushed Toward Continental Crust

Plate Boundaries in Yellow

C. Types of Plate Boundaries 1. Divergent boundaries occur where two lithospheric plates are moving apart. Iceland is at Two Plate Boundaries

a. A rift valley is created at the boundary. b. Fracture zones lie adjacent to the valley.

2. Convergent boundaries are where two plates are moving toward each other. a. Subduction boundary occurs where an ocean plate is going underneath another plate. Andes Mountains were formed as a result of subduction

Mariana Trench b. Deep-sea trench forms where subduction occurs. c. The deepest parts of the ocean are at these trenches. 1) Mariana Trench is 36,201 feet deep. 2) Located off eastern coast of Japan 3) Pressure is 8 tons psi 4) It is 1580 miles long and 43 miles wide.

d. Collision boundary is where two continents collide. 1) This collision causes the crust to be pushed into a mountain range. 2) India is pushing into China at a rate of 5 cm/yr. 3) This is creating the Himalayan Mountains. 4) The same process formed the Appalachian Mountains when North America and Africa collided.

3. Transform boundary occurs where plates are sliding past each other. a. Sliding of the North American Plate and the Pacific Plate create the San Andreas Fault. b. Movement along this fault is as much as 5 cm/yr.

2. But it doesn’t explain the enormous force needed to move the lithospheric plates. B. Ridge push occurs from the slope created at the mid-ocean ridge. 1. Gravity causes new crust to slide down the ridge. 2. Molten magma exits at the ridge, becoming new lithosphere.

C. Slab pull is the force that a sinking plate exerts on the rest of the plate. 1. It is thought to be much stronger than ridge push or mantle convection. 2. This occurs at subduction zones.

II. Causes of Plate Movement A. Mantle convection is the movement of heat from deep in the mantle to the lithosphere. 1. This explains the mid-ocean ridge and subduction zones.

III. Plate Movements and Continental Growth A. Reconstructing the Past 1.rock ages 2.magnetic reversals 3.fossils B. Plate Tectonics and Pangaea 1. Formation of Pangaea a. Gondwana stretched between the South Pole and the Equator and would become: 1)South America5) Southern Europe 2)Africa6) Near East 3)India7) New Zealand 4)Australia8) Antarctica b. Gondwana merged with other landmasses to form Pangaea.

2. Breakup of Pangaea a. Landmasses that formed Pangaea begin to break up around 180 million years ago. b. These plates continue to move, and will continue to do so in the future. Earth during the Permian Period (250 million years ago). Note the Position and emergence of India. Earth during the Triassic Period (200 million years ago).

Earth during the Jurassic Period (135 million years ago). Earth during the Cretaceous Period (65 million years ago).

Earth at the present time. Note that India is now a part of Asia.

Projected positions of the continents 30 million years from now.

Movement of Hawaiian Islands is NW at 8 cm/yr

Absolute movements of Earth’s crust by GPS

C. Plate Tectonics and Continental Growth 1.Most continents were much smaller in the past. 2.Processes involved in plate movement have added material to their margins. 3. At the core of each continent is a craton, the first stable rock to form about 2.5 billion years ago. 4. These cratons show what the continents looked like when they were first formed.

North American Cratons

D. Sources of Growth Material 1. Deep Sea Sediments a.Added when subduction occurs. b.Ocean floor sediments may be left behind. 2. Igneous Rock a. Plutons and volcanoes add igneous rock to continents. b. Some islands (Hawaii) are entirely built of igneous rock. 3. River Sediments a.Deltas at the edge of continents add to the land. b.Good example is the Mississippi River. 4. Terranes a. A terrane is a large block of lithospheric plate that has been moved, usually a long way. b. Eventually the terrane is welded to the continent.

Remainder are excess slides.

Looking into the mid-ocean ridge

Fresh lava covered by tube worms from nearby hot-water vent

Black Smoker From Mid-Ocean Ridge

A black smoker has temperatures as high as 403 o C. The “smoke” is made of sulfides that precipitate as they mix with the cold seawater.

Several chimneys at a vent site

Black Smokers From the Galapagos Rift

Another Black Smoker

Black Smoker With Tube Worms

According to Alfred Wegener’s theory, only one super- Continent, Pangaea, and one ocean, Panthalassa, existed About 250 million years ago.

Location of Mid-Ocean Ridges

Cyanognathus, a mammal-like dinosaur

Earth’s Tectonic Plates

Some of North America’s oldest rocks are in cratons.