Chapter 12: Tectonics, Earthquakes, and Volcanism – Flashcards

vertical elevation differences in the landscape. Expression of local height differences of landforms.

describes Earth's surficial form and texture portrayed so effectively on topographic maps-the lay of the land.

coarsest level of landform consisting of the continents and oceans. Huge continental platforms/ocean basins.

coarsest level of landform consisting of the continents and oceans. Huge continental platforms/ocean basins.

intermediate level of landforms for both continental and ocean-basin features. Continental features in the 2nd order relief include Mountain masses, plains, and lowlands. Ex: Alps, Canadian and American Rockies, Sera Nevada, the Appalachians.

Most detailed order of relief includes mountains, valleys, cliffs, hills, and other landforms of small scale. These features are identifiable as local landscapes. Ex: Death Valley, Ohio Rivera

distribution of Earth's surface by area and elevation in relation to sea level o Greatest ocean depth: 36,000ft in a trench called Marionest Trench located in the Philippines.

are also known as Craton are 4 billion years old. Oldest known rock found in Australia. • building continental crust and terranes • f(x) of tectonic activity and weathering and erosion • Continental Shields (exposed craton) • nucleus: ancient crystalline rock (craton - heartland); eroded to low relief and elevation

Region where a craton is exposed at the surface. Generally, old, low elevation heartland regions of continental crust; various cartons (granitic cores) and ancient mountains exposed at the surface. • Formation of continental crust is complex and takes hundreds of million of years. Begins with the magma that originates in the Asthenosphere and wells up along the magma at the mid-ocean ridges (Mg, Fe); low viscosity (flows); erupts at spreading centers (new oceanic crust/floor); spreads to continental edges à subducts • composition of rising magma differs from magma at spreading centers (melt)

a migrating piece of Earth's crust àmantle convection and plate • tectonics (distinct in history, composition and structure) • common in circum-Pacific region (~25% of western NA's growth à accretion of terranes since ~ 190 mya) • e.g. Wrangell Mountains à Wrangellia terranes

o All rock subjected to stress (FORCE): o Three types of Stresses are o Tension (stretching) o Compression (shortening) o Shear (twisting/tearing) Strain is how rocks respond to stress. Strain is expressed in rocks by folding (bending) or faulting (breaking). When rock strata are layered and flat are subjected to compressional forces, they become deformed.

The bending and deformation of beds of rock strata subjected to compressional forces.

Along the ridge of a fold, layers slope downward away from the axis, which is called anticline. Upfolded rock strata, in which layers slope downward from the axis of the fold, or the central ridge.

In the trough of a fold however layers slope downward toward the axis, called a syncline. A trough in folded strata, with beds that slope toward the axis of the downfold. o thrust fault - overturned folds o warping - greater in extent; e.g. isostatic rebound (Canada)

demonstrate crustal movement; relative displacement on adjacent sides of fracture release of sharp energy during fracture - earthquake

when forces pull rocks apart (also known as tension fault) hanging wall - downward drop footwall block - raised side

compression pushing rock

If the fault plane forms a low angle relative to the horizontal fault < landslide probability; Los Angeles (Northridge)

horizontal movement along fault plane; right-lateral vs. left-lateral can create linear rift valleys not cliffs like the other faults linear rift valleys (SA Fault; NA and Pacific plate)

e.g. Basin and Range; Great Rift Valley (parallel series of mountains/valleys) à tensional forces • horst - upward-faulted blocks • graben - downward faulted blocks . One example of a horst and Graben landscape is the Great Rift Valley of East Africa

literally means the birth of mountains. The process of mountain building that occurs when large-scale compression leads to deformation and uplift of the crust; literally, birth of mountains.

1. Oceanic plate-Continent plate collision Orogenesis formed: Andes & Rockies 2. Oceanic plat-Oceanic plate collision Orogenesis: such collision can produce either simple volcanic island arcs such as Japan, and Indonesia 3. Continent plate-Continent plate collision Orogenesis: Here the Orogenesis is mechanical; large asses of continental crust are subject to intense folding, over thrusting, faulting and uplifting. Formation of the Himalaya & European Alps is a result of such compression forces. • Ocean/ocean/continent à thermal • Continent/continent à mechanical

A tectonically and volcanically active region encircling the Pacific Ocean; also known as the "ring of fire". The region of active volcanoes and earthquakes around the Pacific.

: examples of recent stages of mountain building. Each is a titled-fault0block mountain range in which a normal fault on one side of the range has produces a titled mountain landscape of dramatic relief.

• Stress (force) builds strain (deformation) à friction overcome and plates slide past one another (plate boundary) à release of seismic energy • Focus (hypocenter) - subsurface; earthquake initated • Epicenter - surface directly above focus • Aftershock - shake after main quake • foreshock - preceding the main shock

A device that measures seismic waves of energy transmitted throughout Earth's interior or along the crust.

A roman numeral scale from I-XII representing "barely felt" to "catastrophic total destruction"

An open ended, logarithmic scale that estimates earthquake magnitude; designed by Charles Richter in 1935; now replaced by the moment magnitude scale because it did not differentiate between quakes of high intensity. • Log-scale: every unit = 10x increase in wave amplitude; 31.5x increase in energy release

An earthquake magnitude scale. Considers the amount of fault slippage, the size of the area that ruptured and the nature of the materials that faulted in estimating the magnitude of the earthquake-an assessment of the seismic movement. Especially valuable and more accurate in assessing large Earthquakes than Richter scale. • Size of (sub)surface area rupture, fault slippage, nature of materials faulted, ground acceleration

- A concept describing the faulting process in Earth's crust, in which the two sides of a fault appear locked despite the motion of adjoining pieces of crust, but with accumulating strain the rupture suddenly, snapping to new positions relative to each other, generating an earthquake. Fault zone locked due to friction

irregularities located in fault zone providing frictional surface; e.g. rivets. So if the fracture along the fault is isolated to a small asperity break, the quake will be small in magnitude, however if the break involves the release of strain along several asperities, the quake will be greater in extent and will involve shifting massive amounts of crust. San Francisco EQ (1906), Loma Prieta (1989) - not expressed at surface à San Andreas Fault Los Angeles: 7 EQ > 6.0 magnitude - Landers (1992; 7.4); Northridge (1994; 6.8) à all associated with deep thrust faults (~ 18 km foci)

A mountainous landform at the end of a magma conduit, which rises from below the crust and vents to the surface. Magma rises and collects in a magma chamber deep below, erupting effusively or explosively and forming composite shield, or cinder-cone volcanoes. Pipe rising through asthenosphere, upper mantle and crust

A circular surface depression formed by volcanism; built by accumulation, collapse, or explosion; usually located at a volcanic vent or pipe; can be a summit or on the flank of a volcanoes. Forms near summit (depression) • Magma chamber - collection of magma until eruption • Geothermal heat - heat boiling subsurface water (Yellowstone)

molten rock (surface), gases,

pulverized rock and classic materials of various sizes ejected violently during an eruption.

: the second basaltic lava texture that is more fluid than aa. Pahoehoe forms a thin crust that forms folds and appears "ropy" like coiled, twisted rope.

volcanic landform of pyroclastics and scoria(cindery rock, full of air bubbles), usually small and cone shaped and generally not more than < 450 m in height, with a truncated top. Cone shaped hill.

An interior sunken portion of a volcano's crater; usually steep-sided and circular, sometimes containing a lake; also can be found in conjunction with shield volcanoes. Large basin shaped depression

A volcanic eruption characterized by low viscosity basaltic magma and low gas content, relatively gentle, which readily escapes. Lava pours forth onto the surface with relatively small explosions and few pyroclastics; tend to form shield volcanoes. May come from a single vent or from the flank of a volcano, through a side vent.

A symmetrical mountain landform built from effusive eruptions (low viscount magma); gently sloped, gradually rising from the surrounding landscape to a summit crater; typical of the Hawaiian Islands. • gentle, slow production of lava (Iceland, Hawaii; sea floor) • Low viscosity, dark basalt, gases escape (low viscosity) à pours onto surface, • minimally explosive • Kilauea à longest episode (20 years) • Shield volcano - gently sloped à summit crater; height: gradual accretion of lava • Flood basalts - extensive sheets of basalt; e.g. Columbia Plateau (2-3 km thick), • Deccan Plateau (India)

An accumulation of horizontal flows formed when lava spreads out elongated fissures onto the surface in extensive sheets; associated with effusive eruptions; also known as flood basalts. The Columba Plateau of the northwestern U.S. is a result of the eruption of plateau basalts.

A violent and unpredictable volcanic eruption, the result of magma that is thicker (more viscous), stickier, and higher in gas and silica content than that of an effusive eruption; tends to form blockages within a volcano; produces composite volcanic landforms.

A volcano formed by a sequence of explosive volcanic eruptions, steep sided, conical in shape; sometimes referred to as a stratovolcano, although composite is the preferred term. • subduction zones; magma from melt of crust > viscosity, flows poorly (blocks conduits) à traps/compresses gases (pressure) composite volcanoes: steep sided, conical, symmetrical (if single vent responsible) • pyroclastics produced: ash (< 2 mm), dust, cinders, lapilli (< 32 mm), scoria, pumice and aerial bombs • regional à global effects: Mt. Pinatubo à ↑ albedo=1.5% & ↓ NH Temp=0.5oC • Location and Types of Volcanic Activity: • f(x) of hotspot activity and plate tectonics - occurs in 3 locations • subduction boundaries (C-O: Mt St. Helens; O-O: Philippines, Japan) • sea-floor spreading centers (Iceland/mid-Atlantic ridge); rifting • continental (east Africa) • 3. hot spots - individual plumes rise to surface (Hawai'i/Yellowstone)