| A | B |
|---|
| magnitude | the measure of the amoiunt of energ in an earthquake determined by measuring the amplitude of the largest seismic wave |
| intensity | a measure of an earthquake's effect on people, structures, and the natural environment |
| Richter scale | scale used to measure the magnitude of an earthquake |
| modified Mercalli intensity scale | intensity scale used in the United States |
| plate tectonic theory | A theory that states that large, rigid segments of the outer part of the earth are broken into plates and move relative to one another |
| Ring of Fire | An almost continuous chain of vo lcanoes around the edges of the Pacific ocean |
| Mid-Atlantic Ridge | A lchain of volcanoes that extends through the middle of the world oceans |
| Mediterranean-Himalayan belt | Belt of earthquakes that extends west from Indonesia through the Himalayas |
| crust | Outer layer of the earth that is rigid and is composed of a wide variety of rocks |
| mantle | layer beneath the crust which extends from the base of the crust to a depth of about 2900km |
| core | layer of the earth beneath the mantle |
| asthenosphere | the layer beneath the lithosphere |
| lithosphere | outermost layer of earth, with a typical thickness of 18-120 km. The top layer is the crust. |
| convergent plate boundary | boundary that occurs when edges of continental or oceanic plates move toward each other and collide |
| subduction | when one plate slides under another plate |
| divergent plate boundary | boundary that forms where plates separate |
| Mid-ocean ridge | A divergent plate boundary that develops into an underwater chain of volcanoes |
| Transform plate boundary | A boundary that forms where plates slide past each other |
| Stress | The force applied to a given area of rock |
| Elasticity | A property of matter that allows a deformed object to return to its original shape when the force of stress is relaxed |
| Brittle | A propety of matter that causes it to break when the forces acting on it exceed its elastic limit |
| Ductile | A property of matter that allows it to fold when stressed |
| Metamrphose | To change |
| Fault | fractures in the earth's lithosphere along which measurable movement, or displacement, has occurred in blocks of rock on opposite sides of a fracture. |
| Transform fault (strike-slip) | A type of fault that ocurs along a transform plate boundary where rocks on either side of the fault surface are moving past each other without much upward or downward movement |
| Normal fault | A type of fault where rock above the fault surface moves downward in relation to rock below the fault surface |
| Reverse fault | A type of fault where the rocks abovee the fault surface are forced up and over the rocks below the fault surface. |
| Fault creep | When resistance along a fault is low and blocks of rock can slip without faulting. |
