Science Chapter 4
Terms
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- Fault Block Mountains
- form when Earth's crust is stretched by tectonic forces.
- Strike-slip Faults
- rocks on opposite sides of the fault move in opposite directions or in the same direction at different rates.
- plate
- a large section of Earth's oceanic or continental crust and rigid upper mantle that moves around
- Features Caused by Plate Tectonics
- mountains, ocean basins, volcanoes, earthquakes
- Fault
- when rocks break and move along surfaces
- Main Types of evidence for continental drift
- puzzlelike fit of the continents, fossils of the reptile Mesosaurus found in S. America and Africa. This swimming reptile lived in fresh water and on land that was eventually seperated by ocean. The fossil of the plant Glossopteris has been found in Africa, Australia, India, S. America,, and Antarctica. Evidence of fossils of warm weather plants were found in areas of land in the ARctic Ocean. There was evidence of glaciers found in warm and tropical areas. Glacial deposits and rock surfaces polished by glaciers are found in S. America, Africa, India, and Australia. Parts of these continents were covered with glaciers in the past. Similiar rock structures were found on different continents.
- Transform Boundaries
- two plates slide past one another without converging or diverging. The plates stick and then slide, mostly in a horizontal direction, along large strik-slip faulty.
- Tension Forces
- are forces that pull apart and stretch Earth's crust.
- Reverse Fault
- the rock layers above the fault surface move up relative to the rock layers below the fault. EX: Appalacian Mountains.
- Transform boundary
- occurs where two plates slide past one another. They move in opposite directions or in the same direction at different rates. Earthquakes occur when on plate suddently slips past another. EX: San Andreas Fault in California
- asthenosphere
- plasticlike layer below the lithosphere. The rigid plates of the lithosphere float and move around on the asthenosphere.
- Satellite Laser Ranging System
- a method using lasers and a satellite that measures the exact movements of Earth's plates and which proves there is as little as 1 cm to 12 cam per year of movement.
- Evidence of plates motion...
- earthquakes, volcanoes,and mountain ranges
- Sound Waves
- used on moving ships to map large areas of the ocea floor in detail. Sound waves echo off the ocean bottom - th elonger the sound waves take to return to the ship , the deeper the water.
- Divergent Boundary
- the boundary between two plates that are moving apart. EX: Mid-Atlantic Ridge
- lithosphere
- rigid layer of a plate that is aobut 100 km thick and is usually less dense than material underneath.
- Alfred Wegener
- a German meteorologist that suggested that all the continents were joined together at some time. He proposede the hypothesis of continental drift.
- Mid-Ocean Ridges
- located using sound waves they are an underwater system of ridges, or mountain and valleys. In some of these ridges, vocanic eruptions and earthquakes occur from time to time. These underwater mountain ranges stretch along the center of much of the Earth's ocean floor.
- Subduction
- the area where an oceanic plate goes down into the mantle - where oceanic and continental plates collide. The oceanic plate plunges beneath the less dense continental plate.As the plate decends, molten rock forms and rises toward the surface, creating volcanoes.
- When plates move, they can interact in several ways...
- they can move toward each other and converge, or collide. They can pull apart or slide alongside one another.
- Convergent Boundary
- the place where two plates move together. Earthquakes are common at these boundaries
- Sea Floor Spreading
- Harry Hess, a scientist, proposed that hot, less dense material below Earth's crust rises toward the surface at the mid-ocean ridges. It flows sideways, carrying the seafloor away from the ridge in both directions. As the seafloor spreads apart, magma is forced upward and flows from the cracks. It becomes solid as it cools and forms new seafloor. This denser, colder,seafloor sinks, helping to form the ridge.
- "Pangaea" means...
- all land
- Island Arcs
- chain of volcanic islands that form when two oceanic plates converge and the denser plate is forced beneath the other plate.
- Continental Drift
- continents moved slowly to their current locations as they were once connected as one large landmass that broke apart about 200 million years ago
- Plate Tectonics
- Earth's crust and part of the upper mantle are broken into sections. These sections, called plates, move on a layer of the mantle.
- Earthquakes
- when plates suddently move, vibrations are generated inside Earth that are felt
- Convection Current
- the entire cycle of heating, rising, cooling, and sinking that occurs in the mantle is thought ot be the force behind plate tectonics.
- Evidence for Sea Floor Spreading
- it was discovered that the youngest rocks are located at ridges and become increasingly older farther from the ridges. Also, magnetic alignment of rocks in alternating strips that run parallel to ridges, indicates reversals in Earth's magnetic field.