Plate Tectonics

Raisin Theory

• The outdated idea that Earth contracted due to cooling after the big bang.

• The pressure from the contraction allowed the crust to rise and form mountains and ocean basins.

Isotasy

• The state of balance and equilibrium that exists within the Earth‘s crust.

• The upper lithosphere floats on denser magma beneath.

Clarence Edward Dutton

• American seismologist and geologist.

• Proposed the term isotasy.

Tectonic Plates

• Derived from the Greek word ”tekton” which means carpenter or builder.

• They describe the movement of the lithosphere.

• They describe the physical plates that are massive slabs of solid rock that surround the Earth’s surface.

Plate Tectonics Theory

• The unifying theory of Geology.

• They propose that the lithosphere is divided into 7 major plates and some minor ones.

• The said plates glide above the asthenosphere at a rate of 1-15 cm a year.

What does the Plate Tectonics Theory explain?

• Changes in the surface of the Earth thru time.

• Earthquakes

• Volcanic activities

• Location of mountain ranges.

Continental Drift Theory

• Made by Alfred Wegener, a German scientist.

• Proposed that there was one large supercontinent called Pangaea (“all Earth”) existed during the Permian period.

• It began to break up about 225 to 200 million years ago.

• Though the reason isn’t identified, they slowly drifted away from one another.

Panthalassa

A vast ocean that surrounded Pangaea.

Tethys sea

Separated the two continents.

Iceland

• The world’s only inhabited island where tectonic plates and ocean ridges are seen on land.

• Located on the tectonic plates of Europe and North America.

• This results in Iceland being a geologic hotspot.

Tertiary Plates

Plates that have broken off and continue being broken up from primary or secondary plates.

Crustal Plates

Earth consists of 58 crustal plates and fifteen are identified as major plates (primary and secondary.

Seven Primary Plates

1. African Plate

2. Eurasian Plate

3. Indo-Australian Plate

4. North American Plate

5. Pacific Plate

6. South American Plate

7. Antarctic Plate

Primary Plates

Comprise the majority of the world’s major continents’ landmass and most of the surface area of Earth’s ocean.

Secondary Plate

1. Caribbean Plate

2. Scotia Plate

3. Arabian Plate

4. Indian Plate

5. Philippine Plate

6. Juan de Fuca Plate

7. Cocos Plate

8. Nazca Plate

What is responsible for some of the Earth’s most dramatic geological events?

Tectonic activity

The plate floats on the _ and slides horizontally over it.

asthenosphere

One plate can carry both crusts…

Continental and oceanic

At what rate do tectonic plates move?

Very slow

Where do tectonic activities take place?

Tectonic plates

Lithosphere

The main layer involved in tectonic activities

Two types of lithosphere associated with their respective crusts

Oceanic and continental

Continental Crust

• Made up of lower-density materials, like granitic rock

• Has several deposits that vary in age

• Thickness ranges from 10-70 km

Continental Crust (Basement Rock)

• Oldest foundation (4 BYA)

• A mixture of granite and volcanic rocks.

Cratons

• Platforms connected to basement rocks

• Often survive the cycles of merging and rifting continents

• Generally found in the interiors of tectonic plates

Continental Margins

• Composed of sedimentary rocks

• At the edges of cratons

What is Oceanic Crust made of?

Basalt and gabbro rocks

How old is Oceanic Crust?

Younger than the continental crust, where the oldest age is 200 MY.

How thick is the Oceanic Crust?

7 kilometers

How is Oceanic Crust formed?

Formed by magma from volcanic eruptions that occurred underwater.

What is the Oceanic Crust’s lifespan like?

It’s limited because it is pushed beneath the continental crust.

Continental Crust is made up of…

Granitic and composed of rocks rich in sial (silica and aluminum)

Oceanic Crust is made up of…

Basalt and rocks made up of sima (silica and magnesium)