Plate Tectonics Lecture Exam

What are the main layers of the Earth (outside to inside)?

Atmosphere → Lithosphere → Asthenosphere →Mesosphere → Outer Core → Inner Core

What is the lithosphere made of?

Earth's crust and uppermost mantle; rigid and broken into tectonic plates.

What is the asthenosphere?

Plastic-like layer under the lithosphere that allows plates to move.

Lower mantle; solid but flows slowly, driving convection currents.

What is the outer core made of?

Liquid iron and nickel; generates Earth's magnetic field.

Why does the inner core remain solid despite high temperatures?

Immense pressure and density keep it solid.

What role does the inner core play?

Stabilizes Earth's rotation and maintains the magnetic field.

What gases make up Earth's atmosphere?

~78% nitrogen, 21% oxygen, 1% other gases.

What is the theory of plate tectonics?

Earth's surface is broken into plates that move due to mantle processes.

What is seafloor spreading?

New crust forms at mid-ocean ridges as magma rises and older crust moves away.

What happens at subduction zones?

Dense oceanic plates sink beneath less dense plates, recycling crust.

What evidence supports seafloor spreading?

Symmetrical rock ages and magnetic striping on either side of ridges.

What are the three main driving forces of plate movement?

Mantle convection, slab pull, ridge push.

What is slab pull?

Gravity pulls a sinking, denser plate into the mantle at subduction zones.

What is ridge push?

Gravity slides plates away from the elevated mid-ocean ridge.

Who proposed continental drift?

Alfred Wegener, early 1900s.

What evidence did Wegener use?

Fossils, rock formations, glacial deposits, and continents fitting like puzzle pieces.

Why was Wegener's idea rejected?

He could not explain how continents actually moved.

What technology later supported plate tectonics?

Ocean floor mapping, GPS measurements, and seafloor spreading evidence.

What caused Japan's 2011 tsunami?

A 9.0 earthquake at a subduction zone in the Pacific Ocean.

How high were the tsunami waves in 2011 Japan?

About 9 meters (30 feet).

What is the Ring of Fire?

A region around the Pacific with many subduction zones, volcanoes, and earthquakes.

What is the Mariana Trench?

The deepest part of the ocean, ~36,000 ft deep, located near the Philippines and Japan.

What is stored energy in tectonic plates released as?

Earthquakes

What are the three types of plate boundaries?

Divergent (move apart), Convergent (collide), Transform (slide past).

Example of a transform boundary?

San Andreas Fault (California).

Example of a divergent boundary?

Mid-Atlantic Ridge.

Example of a convergent boundary?

Himalayas (continental collision) or Mariana Trench (oceanic-continental subduction).

What does the Richter scale measure?

Magnitude (energy released) of an earthquake.

What does the Mercalli scale measure?

Intensity and damage caused by an earthquake.

How does the Richter scale increase?

Each whole number is 10× greater shaking, ~32× more energy.

Magnitude ranges on Richter scale?

8.0+ = Great
7.0-7.9 = Major
6.0-6.9 = Strong
5.0-5.9 = Moderate
4.0-4.9 = Light
3.0-3.9 = Minor
Below 3.0 = Very minor

How fast do plates move on average?

A few centimeters per year.

What is the composition of the crust?

Oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium.

How long does it take for crust to move one mile?

~100,000 years.

What is the "epicenter" of an earthquake?

The point on Earth's surface directly above where the quake starts.

What is the supercontinent that appeared?

Pangea