Chapter 13 Flashcards
MINERAL
Inorganic natural solid compound having a specific chemical formula and usually possessing a crystalline structure
CRATON
All continents have a nucleus of ancient crystalline rock on which it grows through the addition crustal fragments and sediments
CONTINENTAL SHIELD
A large region where a craton is exposed at the surface
PASSIVE MARGIN
Where two plates are joined together, where they move as a single mass.
What is the driving force behind plate motion?
- convection currents in the mantle
- grab hold of the underside of the crust (plates) and drags it along
Plate Margins
Where plates meet
3 TYPES:
- Convergent
- Divergent
- Transform
Convergent Plate Margin
Where plates collide head on
Faulting
When a rock breaks
Folding
When a rock bends
Earthquake
An earthquake is a sudden shaking of the ground due to a release of energy deep inside the Earth
Focus
The place in the ground where energy is released and where the earthquakes originate
Epicenter
The place on the surface directly above the focus
Divergent Plate margin
Where plates are moved apart
Transform margin
Where plates are moving past each other in a side to side motion
“P” or Primary Waves
Causes objects at the surface to move side to side
aprox. 8km/s
- faster
- cause things to go back and forth sideways
“S” or Secondary Waves
Causes objects at the surface to move up and down
aprox. 5km/s
- slower
- these cause things to sway
Liquefaction
The fluidization of water-saturated sediment when it is shaken.
- loss of strength and stiffness in response to stress, in this context, an Earthquake
RELIEF
difference between high and low.
Elevation differences in a local landscape; an expression of local height differences of landforms
TERRANE
A rock body formed at one location and moved to another by plate motion.
(example: insular belt in BC, including Vancouver island)
TYPES OF STRESS
(THREE TYPES)
- Compressive Stress
- Tensional Stress
- Shear Stress
COMPRESSIVE STRESS
- forces are directed inward.
- causes shortening
- creates symmetrical folds
- folding caused: anti cline (hump is on top) r syncline fold (hump on bottom)
- faulting caused: reverse fault (one rock body has moved up and over the other rock body which has moved down and under.
TENSIONAL STRESS
- forces are directed outward
- causes stretching, maybe thinning
- folding caused: no folding
- faulting caused: normal fault
- because of tensional stress one rock body has moved down and away from the other which has moved up and away
SHEAR STRESS
- forces are opposite to one another in a side-by-side motion
- causes twisting or tearing
- folding caused: asymmetrical anticline, asymmetrical syncline
- faulting caused: Right lateral/left lateral strike-slip fault
List Historical Eruptions
- Mt. Mazama (Crater Lake, Oregon.) (6,600 years ago)
- Mt. Vesuvius, Italy (Burial of Pompeii) (2,000 years ago)
- Mt. St. Helen (Washington State (May 18, 1980)
- Mt. Dinatubo Philippines, (1991)
Volcano
a volcano is a hill or mountain that forms on the Earth’s surface over a hole in the crust; out of which comes lava (liquid rock), gas (water) and pyroclastic debris (rock fragments such as ash)
Pyroclastic Flows
a fast moving avalanche of hot rock and gas that is very destructive.
Harmonic Tremors
Seismic energy releases associated with volcanos.
- many small earthquakes around the magma chamber that suggest a change in the behaviour of the volcano and the possibility of an eruption.
Lahar
Debris flow caused by a volcanic eruption.
- moderately fast flow of wet sediment that follows the pre-existing drainage of the land.
TYPES OF VOLCANIC ERUPTIONS
- Explosive
2. Non Explosive (Effusive)
EXPLOSIVE ERUPTION (6 characteristics)
- Located on a continental plate
- Rock type is felsic
- Lava viscosity is high (flows slower)
- Rate of gas escape is low, until it erupts suddenly
- Duration of eruption is faster
- Frequency of eruption is rare
EFFUSIVE (NON-EXPLOSIVE) ERUPTION (6 characteristics)
- Located on an oceanic plate
- Rock type is mafic
- Lava viscosity is low, (flows easily)
- Rate of gas escape is faster (gas escaping constantly)
- Duration of eruption is longer
- Frequency of eruption is common
TYPES OF VOLCANOS BASED ON APPEARANCE
- Strato
- Shield
Strato Volcano (composite volcano)
Tall, steep-sided, prominent structure like Mt. Baker.
- composed of layers of lava and pyroclastic debris
- weak internal structure that makes the volcano prone to failure
Shield Volcano
Low and wide, gently sloping dome or “inverted shield shape” composed of layers of lava.
-This makes for a stronger structure less prone to failure
