Plate Tectonics

Explain how how fossil clues provide evidence for continental drift. Use no more than three sentences.

Fossils of similar species are found in continents of South America, Africa, and Antarctica. This suggest that these continents had different climates back then and moved to where they are now which is why climate is different. Some animals fossils, that only reside in 1 area, are found in multiple areas, including out of their continent.

What is Pangea and what happened to it?

Pangea is the name given to a super continent that began to break apart approximately 200 million years ago.

What is a mid-ocean ridge How do mid-ocean ridges form? How do plates move at mid-ocean ridges?

A mid-ocean ridge is long, narrow mountain ranges on the ocean floor formed by magma at divergent plate boundaries. They form by magma cooling at divergent plate boundaries. Plates move at mid-ocean ridges because younger sediments are pushing the older sediments farther away from the ridge.

Describe "basal drag" and explain how this force drives plate tectonics.

Basal drag is caused from convection currents in the mantle. It acts like conveyer belts in the grocery store and drags the lithosphere which is how it drives plate tectonics.

Name the three forces that help drive plate tectonics.

Basal drag, Ridge push, and slab pull.

What is continental drift and who proposed the hypothesis?

Continental drift is the movement of Earth's continents over time. It was proposed bu Alfred Wenger.

What is the difference between normal and reversed polarity?

During normal polarity, a compass needle points north. But during reversed polarity, a needle points south.

Explain how ancient climates provide evidence for continental drift. Use no more than three sentences.

In continents, including South America, Africa, India, and Australia, scientist have found deep starches and glacial groves in rocks. This means that glaciers left these when they were melting. This might mean that parts of these continents were one glaciers but then melted because of continental drift.

What is a magnetic reversal?

Magnetic reversal is an event that causes a magnetic field to reverse direction.

Explain how rock and mountain ranges provide evidence for continental drift. Use no more than three sentences.

Mountain ranges in North America and Europe seem to make one large mountain range. Also, rocks in the east side of South America and the west side of Africa are both volcanic, have similar age, and have similar composition. This might means that theses continents were once connected and had 1 mountain range but then got split up into two by continental drift.

How does new oceanic rock show these magnetic reversals?

New oceanic rock shows these magnetic reversals by aligning its self with Earths' magnetic field.

How fast do plates move? Name and describe the current technology that is used to measure plate movement.

Plates move approximately a few centimeters a year. The current technology used to measure plate movement is the Global Positioning System. This is a system of satellites that orbit earth and track the speed of the plates.

Why did scientist reject the continental drift hypothesis when it was proposed?

Scientist rejected this because they believe that there is no force strong enough to move continents.

What is seafloor spreading? What causes seafloor to spread?

Seafloor spreading is the process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust move away from the ridge. Magma cooling and crystallizing which forms new oceanic crusts causes seafloor to spread.

Describe convergent plate boundary and state what activity and landforms occur there.

The boundary between two plates that movie toward each other. When theses plates collide, many things can happen. If an ocean plate collides with a continental plate, the ocean plate sinks because it is denser and creates a deep ocean trench. The same happens when two oceanic plates collide, the older and denser plate sinks. But when two continental plates collide, the don't sink. Mountain just build up from there.

Describe transform plate boundary and state what activity and landforms occur there.

The boundary between two plates that slide past each other. Earthquakes occur from this because when these plates are sliding, they can get stuck. This builds lots of stress and once released can cause earthquakes.

Define convection.

The circulation of particles within a material caused by differences in thermal energy (temperature) and density.

Describe divergent plate boundary and state what activity and landforms occur there.

The divergent plate boundary occurs when plates separate. This can occur in the middle of a continent or in the middle of an ocean. When theses plates separate, it creates rift valleys.

Explain how the fit of the continents provide evidence for continental drift use no more than three sentences.

The fit of the continents provide evidence for continental drift because each continental coastline seem to match up with each other. Wenger realized the similarities in each of the continental coastline and proposed a theory. These continents seem to fit together like puzzle pieces.

List four evidences of continental drift that were proposed by Wenger.

The fit of the continents, rock clues, climate clues, and fossil clues.

Explain how the magnetic reversals provide evidence of seafloor spreading.

The magnetic reversals provide evidence of seafloor spreading because the stripes reveal a parallel pattern which means that the crust in the mid-ocean ridge is being carried the opposite way.

List three evidences of seafloor spreading. What do all these three evidences indicate is happening?

The magnetic stripes on the ocean floor reveal a parallel pattern, the temperature is greater in the mid-ocean ridge than farther away form the ridge, and sediments closer to the mid-ocean ridge are younger and less dense to the ones farther away.

Define subduction. What do we call the plate that subducts beneath the less dense plate?

The process that occurs when one tectonic plate moves under another tectonic plate. We call it the subduction zone.

Describe "slab pull" and explain how this force helps drive plate tectonics.

The process that results when a dense oceanic plate sinks beneath a more buoyant plate along a subduction zone, pulling the rest of the plate that trails behind it. This helps drive plate tectonics because pulls the rest of the plate behind it when a dense oceanic plate sinks beneath a more buoyant plate.

Describe "ridge push" and explain how this force helps drive plate tectonics.

The process that results when magma rises at a mid-ocean ridge and pushes oceanic plates in two different directions away from the ridge. This pushes plates two different directions away form the ridge and helps drive plate tectonics.

Explain how dating sediments on the ocean floor provides evidence of seafloor spreading.

The sediments located near the mid-ocean ridge are younger and less dense than the ones outside. This might mean that these younger and less dense sediments were newly created because of the magma stored beneath the ridge.

Explain how the temperature of the ocean floor provides evidence of seafloor spreading.

The temperature in the mid-ocean ridge is greater than the abyssal plain. This might mean that magma is located under it and forms the new crust and expands the seafloor.

Define plate tectonics.

Theory that Earth's surface is broken into large rigid pieces that move with respect to each other.

Describe the tectonic plates.

These plates are large masses that move because of the layer right below them, the asthenosphere. When these plates move, earthquakes can happen, mid-ocean ridges can form, and it can create a chain of volcanoes. They are "floating" on the asthenosphere.

When scientists mapped the ocean floor, what significant landform did they find?

They found vast mountain ranges that stretched deep below the ocean's surface.

What technology was used to map the seafloor? How does it work? When did they first use this?

They used an echo sounder. Scientist used this because it sent sound waves down the ocean floor and back. If the sound waves took longer to come back, they can tell that part of the ocean is deeper. They first used this during World War II in the late 1940s.

Describe the convection current that occurs in the mantle.

When materials are heated, the become less dense and expand. Hot mantle material rises upward and makes contact with the crust. Thermal energy is transferred to the cooler surface. It cools, becomes denser, sinks, and contracts and is repeated once again. That is a convection current.

Describe the convergent ocean to ocean boundary, what activity and landforms occur.

When these plates collide, the older and denser plate subducts under the younger and less dense plate which creates a deep ocean trench. And a line of volcanoes called an island arc.

Describe convergent continent to continent boundaries, what activity and landforms occur.

When these plates collide, they don't sink like the ocean to continent or the ocean to ocean boundary, instead rocks are uplifted and it creates mountains such as the Himalayas.

Describe convergent ocean to continent boundaries, what activity and landforms occur.

When theses plats collide, the oceanic plate, because it is denser, sinks beneath the edge of a continent called a deep ocean trench. A A line of volcanoes form above the sub-ducting plate on the edge of the continent.