Study guide feb 14th

fault

A break in the earth's crust

sesmic waves

vibrations that travel through Earth carrying the energy released during an earthquake

secondary waves

waves that travel outward from an earthquke's focus and move through Earth by causing particles in rocks to vibrate at right angles to the direction of the wave

primary waves

1st wave, P, travels the fastest, back-and-forth waves, move through solids, liquids, and gases

Magma

A molten mixture of rock-forming substances, gases, and water from the mantle

Seismologist

A scientist who studies earthquakes

composite volcano

A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials

Locating an earths epicenter

An instrument called a seismometer measures ground motion and is recorded on a seismogram (Graphical illustration of a seismic wave). Seismologists use a method called triangulation to locate the earthquakes epicenter. This method uses speed of seismic waves to determine the distance from the epicenter from three seismometers.

seismic waves

During an earthquake, a rapid release of energy along a fault produces seismic waves. Seismic waves travel outward in all directions through rock. Seismic waves transfer energy through the ground and produce the motion that you feel during an earthquake. The energy released is strongest near the epicenter. As seismic waves move away from the epicenter, they decrease in energy and intensity. The farther you are from an earthquake's epicenter, the less the ground moves.

Earthquakes focus and epicenter

Earthquake Focus and Epicenter When rocks move along a fault, they release energy that travels as vibrations on and in Earth called seismic waves. These waves originate where rocks first move along the fault, at a location inside Earth called the focus. The epicenter is the location on Earth's surface directly above the earthquake's focus.

what are Eathquakes

Earthquakes are the vibrations in the ground that result from movement along breaks in Earth's lithosphere. These breaks are called faults. The forces that move tectonic plates also push and pull on rocks along the fault. If these forces become large enough, the blocks of rock on either side of the fault can move and cause a destructive earthquake.

How do earthquakes form

Earthquakes result from the buildup and release of stress along active plate boundaries. Deep Earthquakes result from convergent plate boundaries. Earthquakes that occur along convergent plate boundaries typically release tremendous amounts of energy. They can also be disastrous. Shallow earthquakes are common where plates separate along a divergent plate boundary and result in smaller Earthquakes

Seismometer

Instrument used to measure horizontal or vertical motion during an earthquake.

Viscosity

Liquids ability to flow

Lava

Magma that reaches Earth's surface

Epicenter

Point on Earth's surface directly above an earthquake's focus

Determining an earthquakes magnitude

Scientists use a scale called a Richter scale to determine the magnitude of an earthquake. The scale begins at 0 and has no upper limit. Each increase of 1 on the scale represents 10x the amount of ground motion recorded on a seismogram. For example, a magnitude 6 will have 10x greater shaking than a magnitude 5. The greatest magnitude ever recorded was a 9.5 in Chile in 1960

Mapping earths interior

Seismologists (scientists that study Earthquakes) Use the properties of the seismic waves to map the Earth's Interior (What the Earth looks like inside). The seismic waves changes speed and direction depending on the material they travel through. By comparing the measurements and the densities of the Earths materials they have determined the composition of Earth's layers.

Types of faults

Strike-slip faults can form along transform plate boundaries. There, forces cause rocks to slide horizontally past each other in opposite directions. In contrast, normal faults can form when forces pull rocks apart along a divergent plate boundary. At a normal fault, one block of rock moves down relative to the other. Forces push rocks toward each other at a convergent plate boundary and a reverse fault can form. There, one block of rock moves up relative to another block of rock.

focus

The point beneath Earth's surface where rock breaks under stress and causes an earthquake

eathquake

The shaking that results from the movement of rock beneath Earth's surface.

What's a rock deformation

When a force is applied to a body of rock it might bend or break. When a force such as pressure is applied to rock along plate boundaries, the rock can change shape. This is called rock deformation. Eventually the rocks can be deformed so much that they break and move.

Types of seismic waves

When an earthquake occurs, particles in the ground can move back and forth, up and down, or in an elliptical motion parallel to the direction the seismic wave travels. Scientists use wave motion, wave speed, and the type of material that the waves travel through to classify seismic waves. The three types of seismic waves are primary waves, secondary waves, and surface waves.

Faults

When stress builds in places like a plate boundary, rocks can form faults. A fault is a break in Earth's lithosphere (outer Layer) where a piece of rock moves toward, away from, or past another. When rocks move in any direction along a fault, an earthquake may occur. The direction that rocks move on either side of the fault depends on the forces applied to the fault.

valcano

a cone-shaped hill or mountain around this opening, built up of the material that is forced out.

shield volcano

a wide, gently sloping mountain made of layers of lava and formed by quiet eruptions

surface waves

seismic waves that travel along the Earth's surface

Seismogram

the record of an earthquake's seismic waves produced by a seismograph

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