Glossary of The Dynamic Crust

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Does the density, temperature and pressure of Earth increase or decrease with depth?
It increases with depth.
What is the Richter Scale?
A numerical scale of magnitude of an earthquake or the amount of energy released. It uses a scale from 0-9. Each number is releases 30 degrees more energy then the previous number on the scale.
What is Earth's core mainly composed of?
It is composed of iron and nickel
What is tha skaking of the ground during an earthquake caused by?
It is caused by the sudden release in energy in the rocks beneath earth's surface.
What is tilted strata?
When once-horizontal layers orf rock are now tilted at an angle to earth's surface.
What is a p-wave ?
It is a compressional wave caused by an earthguake that is like a sound wave causing rocks to move back and forth. Able to travel though liquids, solids, and gases. First to reach a seismic station.
What is an s-wave?
A secondary wave is a transverse earthwuake wave which are similar to waves produced in a rope shaken vigorously. Cause rocks particles to vibrate at right angles in the direction in which the wave is traveling. They are slower then P-waves and cannot travel though liquids and gases.
How can you determine the distance of an epicenter from a seismograph station?
You must determine the distance from three seismograph stations, then draw a circle showing the radius equal to each distance. Where the circles meet is the epicenter.
What is the continental crust composed of mainly?
What are convergent boundaries?
when two plated move toward each other. Mountains are produces when two continental plates meet.
What is the epicenter?
The point on Earth's surface directly above earthquake focus.
What are rift valleys?
They are formed by mid-ocean ridges which is marked by high heat flow and basaltic volcanism.
What is the instrument used to detect and record earthquakes?
The Seismograph.
What are L-waves?
Long waves are waves thart travel alondg earth's surface at relatively slow speeds.
What are hot spots?
Hot spots or Mantle Plumes are alreas of active volcanism in the lithosphere.
What is normal strata?
When sediments are layered horizontally.
What are fracture zones?
Where the ridges are broeken into segments by faults
What suggests minor changes in Earth's crust?
exposed rock strata
Why is the Modified Mercalli scale not always accurate?
The Mercalli Scale which ranges from I to XII is based on the descritions of Earthquake damage. This is not always accurate because damage estimates are subjective.
What is reversal of magnetic polarity?
At one time the Earth's magnetic polarity was opposite then it is now.
When does Subduction occur?
When an ocean plate and a continental plate converge. The boundary between the two plates is called a subduction boundary.
What is the asthenosphere?
It is under the lithosphere, includes the upper mantle and behaves like a thick plastic fluid.
Sediment basins, mid-ocean ridges, ocean trenches, and regions of frequent earthquake and volcanic activity are evidence of what?
Major crustal changes which occur over long periods of time such as continental drift.
What is the driving force behind plate movemnets in the lithosphere?
Mantle convection currents
Where do earthquakes usually occur?
mid-ocean ridges, ocean trenches, along faults, and near margins of tetonic plates.
What are diverging boundaries?
Occurs where two plates move apart from each other.
What is the circum-pacific belt?
A ring of volcanoes and earthquakes that circles the rim of the Pacific Ocean. Also known as the Ring of Fire.
What are normal faults?
when one section of rock moves down relative to the section on the other side of the fault.
What is the movement of the solid rock of Earth's crust called?
What is folded rock strata?
Rocks layers that have been bent or wrinkled. Anticlines are upward folds while synclines are downward folds
What are reverse faults?
when one section moves upward relative to other section.
What are fractures or cracks in rock formations?
What is the defenition of crust?
The solid outer rock zone of the Earth
What is an earthquake?
The vibration or shaking of earth's crust caused by rapid movement of rocks in the lithosphere.
What are benchmarks?
A marked with exact elevation and date planted into the ground.
What are lateral faults?
Transform or strike-slip faults where movement of the rocks sections is horizontal.
Which of earth's crust is thicker and less dense?
Continental Crust
What is the interface between the crust and the mantle called?
The Mohorovicic Discontinuity or the "Moho" Interface.
When do transform boundaries occur?
When one plate slides horizontally past another along a single fault or group of parallel faults such as the San Andreas Fault in California
What is the point in the crust where the earthquake originates?
the focus
What is the shadow zone of the Earth?
It is the zone where no seismic waves are recieved between 103 degrees and 143 degrees from an earthquakes epicenter
What is evidence of mantle convection cells?
Continental drift, high-temp. heat flows where mid-ocean ridges and mountains are currently forming and low temp. heat flows though swallow basins.
What is a geosyncline?
The term means a badin which can be measured on an earth-sized scale. When sediments are depsosited into the ocean, the weight of it causes the oceanic crust to bow downward.. This way the shallow water is never filled up but remains shallow as long as the crust continues to sink
Do S-waves travel though liquid?
No, S-waves can only travel though solids. This is why the outer core is believed to be liquid.
What is the oceanic crust omposed of?
What propels the plates?
Nothing is proven but
1. The plates might be pushed from the rear
2. The convection currents in the asthenosphere drag along the bottom of plates
3. The descending denser edge pulls the plates from the front as it sinks.
Where are most zones of crustal activity located?
Along the margins of continents or in the middle fo the ocean, seperating crustal plates that make up Earth.
What is continental drift?
Continental land masses have been moving across Earth's surface for millions of years.
Evidence of thisis maninly the fit of continental coastal regions and the correlation of rock, mineral, and fossil evidence.
Who developed the theory that the continents were once part of a supercontinent called Pangea?
Alfred Wegener
True or false: The Earth is undergoing constant change.
True. Their is considerable evidence such as weathering and erosion.
What is sea -floor spreading?
The hypothesis that the sea floor forms out of the mid-ocean ridges and moves away from the ridge. Rock gets older as your move away form the ridge.
What is plate tetonics?
The theory that Earth's crust is divided into a number of large plates. Some plates consist of just ocena floor while ocan carry continental blocks. The plates are seperating , colliding, or sliding past one another.

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