Continental Drift and Tectonic Plates

convergent boundary

What is this tectonic plate?

divergent boundary

What is this tectonic plate?

transform boundary

What is this tectonic plate?

a map maker that first noticed that all the continents would "fit" together.

Abraham Ortelius

proposed the theory of continental drift - the continents are slowly drifting around the earth

Alfred Wegener

The Ring of Fire indicates that volcanoes typically form along the edges of the continents at convergent plate boundaries around the Pacific Ocean.

Are there patterns in volcanoes caused by plate movement?

caused by the lower parts of the mantle being heated by the outer core. This part of the mantle becomes less dense and rises to the surface. The mantle comes close to the surface of the Earth, and starts to move horizontally in a parallel motion to the lithosphere. The lithosphere is then dragged with the motion of the mantle. The mantle eventually cools, becomes denser, and descends back down to the lower parts of the mantle.

Convection currents

where two plates move towards each other (collide). The geographical features of the area will vary depending on what two types of plates are colliding.

Convergent plate boundaries

areas where two plates are moving away from each other (divide) . When a divergent boundary is first formed in the middle of a continent, a rift valley will occur (East African Rift Valley). If this continues to occur, a large rift valley will be created and water will start to be held there (Red Sea). Eventually, the two sides will continue to separate and new ocean floor will be made at a mid oceanic ridge (Mid Atlantic Ridge)

Divergent plate boundaries

a crack in the Earth's crust where rocks slide past one another. Different types of faults may form based on direction of plate movement (divergent, convergent, and transform).

Fault

When the plates move, the crust can change shape by moving apart, coming together, or sliding.

How are crustal features related to plate tectonics?

When two plates collide, plate A will push on plate B as plate B will push back on plate A with the same amount of force. The pushing of the plates on one another will result in mountains and other geographical features.

How does Newton's law of action and reaction apply to the Earth's tectonic activity?

The greater the force that is built up in the rock between the plates, the faster the acceleration. This is seen by the size of the earthquakes that are affecting the land.

How does Newton's law of force and acceleration apply to the Earth's tectonic activity?

The plates stay stable and do not move until there is enough force built up to move the plates. This movement is seen and felt as earthquakes.

How does Newton's law of inertia apply to the Earth's tectonic activity?

The distribution of fossils is evidence that supports the theory. Unless continents were once connected, it would be impossible to have the distribution of this evidence to be as exactly matched as it is. The mountain ranges and glacial deposits match up as well. Movement has been proven by sea-floor mapping.

How does historical evidence support the theory of plate tectonics?

a series or chain of mountains that are close together and rise 300 m (1,000 ft.) above its surrounding area (convergent)

Mountain Ranges on Land

underwater mountain ranges where the crust is spreading creating new ocean floor (divergent)

Oceanic Ridges

a large valley shaped area of the earth in which plates of the earth's crust are moving away from each other, forming a system of cracks and faults (divergent)

Rift Zones

that are concentrated on the edges of continents, along island chains, or beneath the sea forming long mountain ranges. More than half of the world's active volcanoes above sea level encircle the Pacific Ocean to form the "Ring of Fire." (convergent)

Ring of fire - volcanoes

has been proven by sea-floor mapping. Sea-floor mapping shows underwater mountain belts called mid-ocean ridges. Mid ocean ridges are places where magma rises to the surface and solidifies, forming new sea-floor, pushing existing rock outwards, away from the ridge. As this happens, the outer edges of the plates are subducted and destroyed as they are pushed into deep trenches, until becoming part of the Earth's mantle again.

Sea-floor spreading

is present at plate boundaries: compression stress at convergent boundaries, tension stress at divergent boundaries, and shear stress at transform boundaries.

Stress

occur when two plates collide and one plate is forced under the other. The subducting plate (the one that goes under) has to be denser or very close to the density of the mantle and denser than the plate it is being subducted under. Since continental plates are alway less dense than the mantle, they cannot be subducted (oceanic plates are subducted under continental plates). Oceanic plates become denser as they age. Therefore, the older oceanic plate will be subducted under the younger oceanic floor (old oceanic is subducted under new oceanic).

Subduction zones

a lowering in the elevation of land. This lower area usually fills in with water (Great Rift Valley in Africa).

Subsidence

occur when two plates slide past one another (slide). Earthquakes are common at transform boundaries. Faults form at transform boundaries (San Andreas Fault)

Transform boundaries

a deep depression of the sea floor caused by the subduction of one plate under another (convergent)

Trench

long, continuous volcanic chain of various mountain ranges (divergent) rising from the ocean floor

Underwater Mountain Ranges

convergent boundaries

Underwater mountain ranges are caused by divergent boundaries and land surface mountain ranges are caused by______ _________

happens when two continental plates collide. Since both are less dense than the mantle they are sitting on, they cannot be forced down. The only place for them to go is up, creating mountain ranges like the Rockies and the Himalayas.

Uplift

Landforms on the crust of the Earth such as mountains.

What are crustal features?

Convection currents in the mantle

What causes movement of the plates?

A well-researched idea or thought that has a substantial amount of evidence to support it. It can still be researched and disproved

What is a theory?

The theory of plate tectonics provides an explanation for how the continents can move. According to this theory, the Earth's outer crust is divided into several plates. These plates consist of the crust and a small amount of the underlying mantle. The plates move due to convection currents within the mantle.

What is the theory of plate tectonics?

Evidence to explain the phenomenon is necessary to have a theory accepted.

What makes a theory accepted or not accepted?

Asthenosphere

Which layer do the pieces of the lithosphere float on?

Lithosphere

Which layer of the Earth contains the tectonic plates?

Pangea

a supercontinent, a large landmass formed by all the continents coming together. Evidence supports the theory that Pangea may have existed approximately 225-260 million years ago. Pangea is from the Greek origin and means "all lands" (or "all Earth")

Alexander du Toit

suggested Pangea did not split all at once, but first split into two landmasses called Laurasia and Gondwana, which later broke apart into today's continents.