Chapter 6 Test Flashcards
Earthquake
Vibrations in the ground that result from movement along faults or breaks in earth’s lithosphere
Fault
A break in earth’s lithosphere
3 types of faults
Normal fault
Strike slip fault
Reverse fault
Normal fault
Forms when forces pull rocks along a divergent plate boundarie; block above fault moves down
Strike slip fault
Two blocks of rock slide horizontally past each other in opposite directions
Reverse
Forces pushes two blocks of rock together with the rock above the fault moving up
Focus
Point beneath earth’s surface where rock under stress breaks to cause an earthquake
Epicenter
Point on the surface directly above the focus
Seismic waves
Waves that carry energy of an earthquake away from the focus
What are the 3 kinds of seismic waves?
Primary waves
Secondary waves
Surface waves
Primary waves (p-waves)
Compression waves that travel through solids and liquids
Secondary waves (S-waves)
Only travels through solids and temporarily changes shape
Surface waves
Moves slower than P and S waves, but can produce severe ground movement with a wavelike motion
Seismometers
Devices that measure and record ground motion and helps determine the distance seismic waves travel (Lag time)
How do you locate an epicenter?
By triangulating the data from at least 3 seismometers
- Find the lag time
- Find the distance to the epicenter
- Use map scale to mark radius on compass then draw circle around each
Volcano
Weak spot in earth’s crust where molten material comes to the surface
Magma
Molten mixture of rock forming substances, gasses, and water from the mantle.
Lava
When magma reaches the surface, it’s called lava
Ring of fire
One major belt formed by many volcanoes that rim the Pacific Ocean
What is a string of islands created by volcanoes near boundaries where 2 oceanic plates collide and one skins beneath the other?
Island arc
What is an area where material from deep within the mantle rises then melts, forming magma?
Hot Spot
Geologists classify eruptions as either:
Quiet or explosive
Quiet eruption
Magma has low silica content, flows easily and erupts quietly with gasses gently bubbling out and lava oosing gently producing both pahoehoe and aa
Explosive eruption
Magma high in silica content, with trapped gasses building up pressure inside until they explode with incredible force creating a pyroclastic flow
Pahoehoe
Hot, fast moving lava
Aa
Cooler, slow moving lava
Pyroclastic flow
An eruption that hurls ash, cinders, and magma bombs
Active volcano could explode anytime,
Dormant volcano not active but may become active
Extinct volcanoes unlikely to erupt again
Lightning forms in volcanoes bc all the ash rubs together causing friction eventually making lightning
Landforms from lava and ash
- Shield volcano
- Cinder come volcano
- Composite volcano
- Lava plateaus
- Caldera
Landforms from magma
Volcanic necks Dikes Sill Batholiths Dome mountain
What is geothermal activity?
Occurs when magma, a few kilometers beneath earth’s surface, heats underground water and forms
Hot springs!
Formed when underground water is heated by a nearby body of magma or hot rock and eventually rises to the surface to collect in an all natural pool
Geyser
Fountain of water that erupts from the ground when buildup of pressure is released
