GEOG 1113 Test 2
A Batholith is ___.
A complex of multiple plutons. Typically originates from deep below mountain ranges and are quite large in scale.
What are 3 things that occur when magma approaches the surface of the earth?
Decrease in pressure (gases released). Bubble formation pushes magma toward surface. Magma can escape onto surface through vents to form volcanoes.
Magma is found _____.
Deep below the earth's surface in the crust.
High viscosity is __&__, while low viscosity is __&__.
Thick & slow, thin & fluidic.
How do waves travel through dense material versus less dense material?
Faster in denser material.
Describe the speed of P waves and what P waves do to rock.
Fastest waves (6-14km/s) therefore first to be detected; compress rock in direction of travel (parallel).
Roughly how quick to Mafic Lava flows travel?
Typically < 10 km/hr (6mph) but can reach speeds of 40 km/hr (25mph).
A Magma Chamber is ____.
Underground pool of magma.
What is an earthquake?
a sudden release of energy stored in rocks; the energy is built up from stress on rocks.
Where/when do earthquakes generally happen?
along fault lines when there is movement; also from volcanoes, magma, landslides, and explosions.
What is a fault-based earthquake?
an earthquake where stress along fault slowly builds up until the stress is built up so high that the rock layers break. Stress is relieved along ruptured fault.
A Laccolith is __.
an intrusion between layers that forces overlying strata to deform upward in a dome shape. (sills are flat, laccoliths are domed) (formed from felsic magma)
What is wave speed dependent on?
density and elasticity of substance traveling through.
What is a sill?
sheet-like intrusion that is parallel to older rock layers. (formed from mafic lava)
What can you tell by examining the P-S wave interval?
distance from an earthquake.
What are induced earthquakes?
earthquakes caused by human activities. Typically low magnitude.
Lava is ___.
extrusive molten rock. pretty much surface magma.
Shield Volcanoes are ___.
frequent, quiet eruptions. Developed from hotspots and create islands.
Flood Basalt is ___.
huge outpourings of mafic lava; can produce large igneous province.
Where are hydrothermal vents typically found?
in regions where magma is close to surface.
Plutons are ___.
large bodies of intrusive igneous rock typically several km in dimension. Often part of all a solidifies magma chamber.
Magma is a complex of ____.
liquid material, small solid crystals, and dissolved gasses; (molten rock)
What is an earthquake cycle?
long-term stress build and relief process.
What is a volcanic neck (or plug)?
magma in a volcano's vent that has solidified; usually deep below the surface.
Extrusive igneous events occur when ___.
magma is released into the surface of the earth. Typically via eruptions.
What is magnitude?
measure of released energy.
Recurrence Intervals are ___.
the average time of stress build.
Where do seismic waves from an earthquake propagate outward from in an earthquake?
the hypocenter.
What is the hypocenter (focus)?
the location where fault first ruptures.
Viscosity is ____.
the tendency to resist flow.
What is liquefaction?
water-saturated sediment that when shaking occurs, sediment behaves like a liquid. Towns and cities built on such sediment are vulnerable to flood, sinking, and coastal reclamation.
Magma is similar in consistency to _____.
wet cement or oat meal.
A Lava Dome is ____.
when felsic lava extruded from vent mounds up; can be destroyed through explosion or collapse.
A Lava Fountain is ___.
when lava is forcefully ejected from a fissure or vent.
A Lava Lake is ____.
Large volume of molten lava contained in volcano's vent crater.
What is intensity?
shaking felt and damage done.
What is a dike?
sheet-like intrusion that cuts across older rock layers.
How many times has magma been encountered?
3
What is a Pyroclastic Flow?
A fast moving cloud of hot gases and ash.
Lava Tubes are ___.
A thick crust that can form above and around a flow path.
A Tephra is ___.
Airborne lava that solidifies before hitting the ground.
What is a Plinian Eruption?
An eruption releasing large eruption column into atmosphere.
A Kipuka is ___.
Area of land surrounded by younger lava flows.
What are some effects from volcanoes on global climate?
Ash and sulfuric acid can block solar insulation. Large eruptions can eject material into stratosphere.
Where are stratovolcanoes most commonly found?
At subduction zones.
How is Tephra classified? What are the 3 types?
By size; Ash (<2mm), Lapilli (2-64mm), Volcanic Bombs (>64mm)
How can the epicenter of the earthquake be located?
By using three separate detection stations to triangulate its location.
How are Plutons and Batholiths typically exposed?
By way of erosion.
Supervolcanoes are ____.
Eruptions ejecting greater than 1,000km^3 (240 mi^3); only 4 have occurred in past 2 million years.
Hydrothermal Vents are ___.
Fissure in Earth's surface where geothermal-heated water emerges.
A Spatter Cone is ___.
Fluid lava flung into air heaps up around vent. Semi solid when lands and welds to other rocks.
Felsic Lava is ___.
High silica content and relatively cool; extremely viscous which typically cause explosive eruptions.
What are the four main factors that control an earthquake's destructiveness?
How shallow it is (more shallow = more destructive) How close to epicenter (closer = more destructive) What type and what size of rock (varies) How large the population is nearby
Mafic Magma facts include ___.
It is basaltic. It is < 50% SiO2 It is 900-1500 C More fluid than viscous.
Felsic Magma facts include ___.
It is granitic. It is 60-75% SiO2 It is < 900 C More viscous.
Characteristics of Mafic Lava flows are ____.
Low viscosity. Gases escape readily (quiet eruptions). Erupt from long fissures. Most common volcanic activity.
Pillow Lava is ___.
Mafic lava extruded underwater.
Igneous Landforms are derived from _____.
Magma
What is the Intensity scale called?
Modified Mercalli Intensity Scale
What scale is used to measure earthquakes today? What is the former scale used?
Moment Magnitude; Richter Magnitude
A Shield volcano is ___.
Mountain built by many layers of fluid lava; low profile but horizontally extensive.
What is Pahoehoe?
Quick flowing lava.
Magma viscosity depends on what 4 factors?
Silica - more causes increased viscosity. Water - more causes decreased viscosity. Volatiles - more causes increased viscosity. Temperature - increase causes decreased viscosity.
What is a stock?
Similar to a batholith, but smaller exposed area; often a small portion of a much larger, still buried batholith.
What is 'A'a?
Slow moving lava flow. Several meters thick that forms a thick crust.
Stratovolcanoes (or composite volcanoes) are ___.
The "classic" volcano; built from multiple layers (strata) of lava and tephra.
What is the scale for measuring volcanic eruption intensity?
The Volcanic Explosivity Index; measured on a scale of 1-8. Similar to the way earthquakes are measured.
What is the biggest danger posed my mafic lava?
The changing of established infrastructure.
What does the P-S wave interval not convey?
The direction from which the earthquake came.
Examples of Igneous Landforms include _____.
Volcanoes, Dikes, and Geysers.
How can humans cause induced earthquakes?
Water in reservoirs can add stress to faults. Hydraulic fracturing injects waste water into ground. Rapid groundwater removal. Geothermal plants pump water into ground.
What are surface waves?
Waves that travel across the surface of the earth. Arrive after P and S Waves. Most destructive type of waves.
A caldera is ___.
a large caldron-like depression resulting from land collapse after a volcanic eruption.
What is the epicenter?
point on earth's surface that is directly above the hypocenter; usually where the strongest shake occurs.
What are the three main types of seismic waves?
primary (P), secondary (S), and surface waves
Describe the speed of S waves and what S waves do to rock.
second wave to be detected (3.6km/s); shears rock side to side or up and down (perpendicular).