Earth Science Final Review 2 - Plate Tectonics

Seafloor spreading

1. Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the Seafloor. 2. Ocean floors are spreading apart due to convection currents in the mantle. Magma from interior of earth is injected at mid ocean ridges resulting in new oceanic crust spreading symmetrically away from mid-ocean ridges.

What is Seafloor spreading?

1. Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. 2. Ocean floors are spreading apart due to convection currents in the mantle. Magma from interior of earth is injected at mid ocean ridges resulting in new oceanic crust spreading symmetrically away from mid-ocean ridges.

What are the 3 pieces of evidence Wegener used to show drift?

1. The continents appear to fit as a puzzle. 2. Ancient Fossils are found on separate continents miles apart. 3. Rocks of the same age and type are on both sides of the Atlantic Ocean.

Know the structure of the earth including crust, lithosphere, asthenosphere, mantle, outer core, and inner core.

4 different layers. From inner to outer - inner core, outer core, mantle, and crust. Hotter as you go in. The lithosphere is a layer that includes the crust and part of the upper mantle. The asthenosphere is just below the lithosphere and is part of the mantle - more like liquid.

Tectonic Plate

A tectonic plate (also called lithospheric plate) is a massive, irregularly shaped slab of solid rock, generally composed of both continental and oceanic lithosphere.

What are convection currents?

Convection currents are formed by hot magma near the core rising towards the surface, while cooler magma near the crust sinks, setting up a current that causes the plates to move.

What is the mechanism of continental drift?

Convection currents.

Know the physical state of each (solid or liquid) and their comparative thickness.

Crust (3-5 miles thick, solid), Mantle (1,800 miles thick, very hot, solid but flows like asphalt - plates float on the mantle), outer Core (metals are in liquid state, 1,400 miles thick - composed of melted nickel and iron), Inner Core (about 800 miles thick, solid)

What are the 3 types of plate boundaries?

Divergent, convergent, transform

How were the Himalayas formed?

Himalayas were formed as a result of the collision of the Indian plate and the Eurasian plate.

Hotspot

In areas where the plates come together, sometimes volcanoes will form. Volcanoes can also form in the middle of a plate, where magma rises upward until it erupts on the sea floor, at what is called a "hot spot."

What is a hotspot?

In areas where the plates come together, sometimes volcanoes will form. Volcanoes can also form in the middle of a plate, where magma rises upward until it erupts on the sea floor, at what is called a "hot spot."

Why does tectonic activity occur in belts?

It is where the tectonic boundaries or edges are. Where two plates are meeting together.

Subduction

One plate (the denser one) sinking under another plate when two plates converge.

Core

Outer core and inner core - last 2 layers of earth. Outer core is liquid and has iron and nickel metals. Inner core made up primarily of iron. Due to high pressure, the inner core is mostly solid.

Transform

Plates are moving side to side.

Ring of Fire

Rim of the Pacific tectonic plate where many volcanos and earthquakes occur.

What is evidence of sea floor spreading?

Rocks near mid oceanic ridge are younger.

Mantle

Second layer of earth - solid but flow like asphalt

How was Hawaii formed?

The Hawaiian Islands were formed by such a hot spot occurring in the middle of the Pacific Plate.

Asthenosphere

The asthenosphere is just below the lithosphere and is part of the mantle - more like liquid. It is where the convection currents in the mantle occurs.

Explain how Earth's magnetic field is produced.

The earth's magnetic field is caused by the outer core of the earth. The outer core is made of liquids and molten metals. Differences in temperatures and density and the Coriolis effect cause currents to form. This creates electric currents producing a large magnetic field.

Why is the earth's magnetic field important?

The earth's magnetic field is important because it deflects cosmic radiation from our sun and other stars. Radiation flies at earth, but our magnetic field goes so far out that it pushes the radiation away from our atmosphere. This is important to our health.

Lithosphere

The lithosphere is a layer that includes the crust and part of the upper mantle. It is where the tectonic plates lie.

Tectonic Plate theory

The theory of plate tectonics states that the crust of the earth is broken up into large pieces, or plates, that move around by floating on top of the liquid layer of the earth known as the mantle

What is continental drift?

Theory that continents were once joined and have now drifted apart. Idea created by Wegener.

Crust

Top layer of earth - solid

Convergent

Two pates are colliding.

Divergent

Two plates are moving away from each other.

Obduction

When continental lithosphere subducts to oceanic lithosphere.