geology 100 exam # 3 study guide

Nuee Ardentes or Pyroclastic flow

("fire cloud") the hot gases roar down the mountain slope instead of up into the atmosphere

Vent

(Central Vent) mail opening at the top of the volcano. -some have secondary vents in & around

Describe how a seismologists determines the location of the epicenter of an earthquake

-Triangulation -D= S x T (distance = speed of wave x time it travels) -3 station reports are needed to locate but only 1 report is needed to determine distance to epicenter

San Andreas Fault

-the boundary between the North American and Pacific plates -Horizontal movement (transform fault) -10% of US population lives near it -"great quake" is produced an average of once every 160 yrs

Name 3 basic seismic waves & 2 facts ab each

1. Primary or P-waves- 1st to reach an area; fastest (6 km/sec); compression pattern in a straight line 2. Secondary or S-waves- move ab 3 km/sec; wavy, side-to-side pattern 3. Surface or L-waves - begin at the epicenter & can only travel on the surface; speed ab 2 km/sec; ocean like wave pattern- most destructive wave

Name & Define 3 earthquake scales

1. Richter Scale- based on the amplitude of largest seismic wave recorded 2. Modified Mercalli Scale- measure the intensity of the earthquake which directly effects humans & surface structures 3. Moment Magnitude Scale (MMS)- most commonly used, estimates/measures the energy released by the quake

List 4 basic types of mountains- type, how it changes, example

1. Volcanic - lava builds up on the land/sea floor creating mnts. examples: cascades, hawaiian isalands, surtsey 2. Dome- magma intrusions invade above rock layers & push up to form dome-shaped mnts called lacccoliths. examples: Ozark Mt. & Stone Mt. 3. Folded-- sediments build up on the ocean floor from the land forming a geosyncline- the pressure from sides raises & folds the rock layers. examples: The Appalachian Mountains & Himalayan Mts. 4. Fault/Block Mts.- land masses shift upward along a fault zone during earthquakes creating steep, jagged mountains. examples: rocky mts & the andes mts.

Name & Define the 3 types of plate boundaries

1. divergent- move away from each other 2. convergent- move against each other 3. transform- 2 plates slip past each other laterally

List 6 major hazards of earthquakes

1. ground shaking & foundation failure 2. fire 3. falling objects 4. liquefaction 5. landslides 6. aftershocks

List 4 major hazards of volcanic eruptions

1. lava 2. Pyroclastic Flow 3. floods, forest fires, & lahars (hot mudflows) 4. volcanic gases & dust, ashes, & cinders

List 6 major types of evidence which Wegener used to support his Theory of Continental Drift *****

1. map fit 2. matching mountain belts 3. paleontology---Mesosaurus 4. glaciation patterns 5. location of climate zones 6. creation of "new mountains"

List 5 methods which are used to forecast volcanic eruptions

1. past eruption patterns 2. earthquake activity 3. temperature changes in rock/water 4. bulging of land at surface (tiltmeters) 5. analysis of radon gas emissions

List 4 important economic benefits of volcanic activity

1. recreation/tourism 2. fertile soils 3. geothermal energy 4. source of valuable minerals

List 5 methods which are used to forecast earthquakes

1. tilting or bulging of surface 2. changes in radon gas emissions 3. changes in groundwater levels 4. unusual animal behavior (china) 5. past earthquake patterns & monitoring fault zones

Geosyncline

A major downwarp in the Earth's crust in which sediments accumulate.

Mount St. Helens

A mountain within the Cascade Mountain Range that runs through the state of Washington. erupted May 18, 1980 and resulted in deaths

Continental Drift

Earth's continents are not fixed in place but move slowly over geologic time due to geological factors like tectonic plates

Lithosphere

Earth's outer layer that varies in both thickness & density depending on if it is oceanic or continental

What is the difference between a Hanging Wall & a Footwall?

Faulting terms --if the miner is divided by the fault plane, he attaches his lantern on the hanging wall (move down relative to the footwall) and his feet are on the footwall

What is the difference between Focus and Epicenter?

Focus - point underground where the earthquake originates. Epicenter- point of the surface directly above the focus (usually the strongest shocks)

Alfred Wegener

German meteoroloigst who formulated the Continental Drift hypothesis in 1912

New Madrid, MO.

Great EQ felt as far as Boston occurred here 3-4 M7 at this area in a two year window

Isostasy

The balancing of the downward force of the crust and the upward force of the mantle.

Subduction

The process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary.

Kilauea Volcano

This Hawaiian shield volcano has been erupting continuously since 1983, most active volcano in the world

Mount Vesuvius

Volcano that erupted in 79 AD that killed many people and buried the city of Pompeii; nuee ardente gases gottem

Fault

a crack in the earth's crust

Rift Valley

a deep canyon-like structure along the crest of some ridge segments; evidence that tensional forces are actively pulling the oceanic crust apart at the ridge crest

Asthenosphere

a hotter & weaker region in the mantle that lies below the lithosphere

Basin

a natural depression in the surface of the land often with a lake at the bottom of it

Monocline

a one sided fold -type of complex fold

Convection Cells

a pattern of convection- upward movement of less dense material & downward movement of more dense material that appears to drive the motion of plates

Mesisaurus

a small aquatic freshwater reptile whose fossil remains are limited to rocks of permain age in South America & Southwestern Africa. an example to back Wegener's argument

Pangaea

a supercontinent that existed about 200 million years ago, during the later paleozoic & early mesozoic eras.

Caldera

an extremely large crater of a volcano -example: Crater Lake National Park in Oregon (Mount Mazama)

Subduction Zone

another name for convergent boundaries, they are sites where lithosphere is descending onto the mantle. It occurs bc the density of the descending lithosphere plate is greater than the density of the underlying asthenosphere

Earthquake

any shaking or trembling in the crust of the earth caused by sudden movement along a fault zone

Submarine Volcanoes

begin as lava eruptions on the ocean floor & form island volcanoes; can develop over a hot spot or on a plate boundary -example: Surtsey off the coast of Iceland (on the Mid-Atlantic Ridge) -special type of volcano

Cindercone

composed of mainly ashes & cinders; usually no lava flows; has a cone shaped mountain w/ steep sides; very explosive eruptions -examples: Sunset Crater near Flagstaff, Arizona & Paricutin, Mexico -1 of 3 types of volcanic peaks

Shield

composed of mainly fluid-like lava; largest in overall size; dome-shaped w/ gentle slope (5-10 degrees); the least explosive -examples: Moana Loa on Hawaii- world's largest & Kilauea on Hawaii (currently active) -1 of 3 types of volcanic peaks

Plate Boundaries

deep faults or cracks in the Earth's crust like the Pacific "Ring of Fire"

Syncline

downward fold of the rock layers -type of fold

Mid-Ocean Ridge

fracture zone between segments of the ridge are transform faults in oceanic crust

Tsunami

giant seismic sea waves created on the ocean floor faults -hazard of earthquake

Krakatau

island volcano in the east indies which self-destructed in 1883; caused the "year without summer" in the U.S.

Fault- Block Mountains

land masses shift upward along a fault zone during earthquakes creating steep, jagged mountains; examples: rocky mts & andes mts

Hot Spots

localized hot areas not associated w/ plate boundaries. Move w/ the plate, so eventually become inactive example: Hawaiian Islands w/ hot spot in the middle of the Pacific Plate

Deep-Ocean Trench

long linear depressions in the seafloor that are generally located a few hundred kilometers offshore of either a continent or a chain of volcanic islands.

Describe 3 major differences between Magma & Lava

magma- 1. deep inside earth 2. formed from high silica minerals (felsic) 3.has great viscosity or thickness (the thicker the more explosive) lava- 1. on or near the surface 2. formed from low silica minerals (mafic) 3. low viscosity or fluid-like (non-explosive)

Composite (Stratovolcano)

most common type; alternates between lava eruptions & ash/cinder eruptions; can be explosive sometimes; the tallest volcanic mountains in height -examples: Mt. Rainer near Seattle, WA, Mount St. Helens, Mt. Vesuvius & Mt. Etna -1 of 3 types of volcanic peaks

Island Arc

new formed land, consisting of an arc-shaped chain of volcanic islands, develops on the overriding plate

Appalachians

on the eastern US; composed of parallel ridges & valleys; it is an example of folded mountains; they are older than the coast

Ring of Fire

plate boundaries exist all around the Pacific Ocean rim; most are subduction zones w/ deep trenches; 75% of all volcanoes lie in the '"Ring of Fire"

Paleomagnetism

rocks that formed thousands or millions of years ago and contain a "record" of the direction of the magnetic poles at the time of their formation

aa Lava

rough, jagged pieces or blocks from slow moving lava

Crater

round, bowl-shaped depression at the top of the volcano

pillow lava

rounded form of lava usually from flows in the ocean

Seismograph

sensitive instruments used to monitor & record earthquake waves.

What does a Seismic Wave Time-Travel Graph show?

shows the time and distance that the P- wave and S-wave are traveling at

pahoehoe

smooth, twisted ropes from fast moving lava

Fault Scarp

steep cliffs at the edge of the vertically displaced block

Liquefaction

subsidence caused by shaken water-saturated ground. -hazard of earthquake

Elastic Rebound Theory

the "physics behind earthquakes" build-up and release of rock stress in the form of waves

Mount Pelee

the 1902 eruption of Mouth Pelee on the island of Martinique in the Caribbean destroyed the city of St. Pierre; The Nuee ardente vaporized 28,000 ppl, only 1 survivor- a criminal

Fold

the bend in layers of rock folding- the bending of crustal rocks due to stress such as lateral compression

Graben

the block drops down between 2 parallel faults. example: death valley

Crustal Deformation

the deformation of the earth's crust; the deformed rocks are solid not molten & are particularly obvious in sedimentary rocks since they originally were deposited horizontal - two primary types of deformation: folding & faulting

Theory of Plate Tectonics

the lithosphere consist of segments & plates, the plates meet along boundaries tht may be 1. divergent (move apart from each other), 2. convergent (move towards each other), or 3. transform (move laterally past each other).

Magnetic Polar Reversals

the magnetic North pole becomes the magnetic South pole and vice versa.

Volcanic Neck

the pipe or "throat" of an old volcano that filled w/ solidified lava after its final eruption. -examples: Shiprock in New Mexico & Devils Tower in Wyoming

Sea Floor Spreading

the process by which new oceanic lithosphere forms as magma rises toward the surface and solidifies creating new seafloor. -the term for the mechanism that operates along the oceanic ridge to create new seafloor

Orogenesis

the process which form mountains on the earth -there are 4 basic types

Seismology

the study of earthquakes and their effects

Horst

uplifted block between 2 parallel normal faults

Anticline

upward fold of the rock layers -type of fold -can develop into traps underground for oil & natural gas deposits- holds economic value- in gulf of mexico

Volcano

usually a mountain landform around an opening (vent) in the Earth's crust where magma reaches the surface as lava.

Flood Basalt

vast accumulations of lava that build up, layer upon layer, on the surface. (also called lava plateaus); possible cause of mass extinctions in the past. -example: Columbia River Plateau on the Pacific Northwest & Yellowstone (closest one to us)

Magnetometer

very sensitive instrument towed by Oceanographers to survey the ocean floor. They reveal signature of seafloor spreading as a symmetrical pattern of magnetic stripes parallel to the axis of the mid-ocean ridge

Fault Zone

weak cracks in the rock layers

Convergent Plate Boundary

when two plates move towards one-another, resulting in either oceanic lithosphere going beneath an overriding plate-eventually to be reabsorbed into the mantle, or possibly in the collision of two continental blocks to create a mountain belt. examples: Andes, Cascades

Transform Plate Boundary

where two plates grind past each other without the production or destruction of lithosphere example:San Andreas Fault

Divergent Plate Boundary

where two plates move apart, resulting in upwelling & partial melting of hot material from the mantle to create new seafloor. example: The Mid-Atlantic Ridge