Results of plate tectonics: 1.volcanism 2.diastrophism 3.earthquakes

Results of plate Results of plate tectonics:tectonics:

1.volcanism1.volcanism2.diastrophism2.diastrophism3.earthquakes3.earthquakes

VolcanismVolcanism

VolcanismVolcanism movement of molten rock from movement of molten rock from

earth’s interior through a conduit earth’s interior through a conduit or opening to, or near, the surfaceor opening to, or near, the surface

Types of volcanism:Types of volcanism:A. ExtrusiveA. Extrusive

1. Volcanoes1. Volcanoes a) shielda) shield b) compositeb) composite c) cinder conec) cinder cone

2. Lava Flows2. Lava Flows flood basaltsflood basalts

B. IntrusiveB. Intrusive

A. Extrusive VolcanismA. Extrusive Volcanism Magma reaches the surface (lava) and Magma reaches the surface (lava) and

cools above the surface.cools above the surface.

1. Volcanoes1. Volcanoes: hills or mountains of : hills or mountains of volcanic material that was released volcanic material that was released under pressure from a ventunder pressure from a vent– >500 active (4/5 “ Ring of Fire”)>500 active (4/5 “ Ring of Fire”)

- subduction, rift valleys, mid-oceanic - subduction, rift valleys, mid-oceanic ridges, hot spotsridges, hot spots

Types of Volcanoes:Types of Volcanoes:a) Shield Volcanoesa) Shield Volcanoes

– broad, gently sloping surfacesbroad, gently sloping surfaces examples: Hawaii, Azores, Mt. Hekla in Icelandexamples: Hawaii, Azores, Mt. Hekla in Iceland

– tallest mountains on earth are shield tallest mountains on earth are shield volcanoes from the ocean floorvolcanoes from the ocean floor

– effusiveeffusive eruption eruption nonviolent eruption due to type of magmanonviolent eruption due to type of magma

– low viscosity; 2200 degrees F, little gas in magmalow viscosity; 2200 degrees F, little gas in magma– Iron, magnesium, low in silica: from Iron, magnesium, low in silica: from asthenosphereasthenosphere

Primarily basaltPrimarily basalt

b) Composite Volcanoesb) Composite Volcanoes– steep-sidedsteep-sided– alternating layers of pyroclastics and alternating layers of pyroclastics and

lavalava pyroclasticspyroclastics: rock pieces ejected:: rock pieces ejected:

– Tephra: pulverized rockTephra: pulverized rock– Scoria: cindery vesicular rockScoria: cindery vesicular rock

– ash falls and lava flowsash falls and lava flows– subduction zonessubduction zones

examples: Mt. St. Helens, Mt. Rainier, Mt. examples: Mt. St. Helens, Mt. Rainier, Mt. Fuji, Mt. HoodFuji, Mt. Hood

– explosive explosive eruption due to type of eruption due to type of magmamagma higher viscosity, 1600 F; contains gaseshigher viscosity, 1600 F; contains gases from melting of from melting of lithospherelithosphere: more silica: more silica

Types of volcanism:Types of volcanism:A. ExtrusiveA. Extrusive

1. Volcanoes1. Volcanoes a) shielda) shield b) compositeb) composite c) cinder conec) cinder cone

2. Lava Flows2. Lava Flows flood basaltsflood basalts

B. IntrusiveB. Intrusive

Composite = stratovolcanoComposite = stratovolcano

Insert map of volcanoesInsert map of volcanoes

CALDERACALDERA: landform associated with : landform associated with some composite volcanoessome composite volcanoes

– large bowl-shaped depression left after large bowl-shaped depression left after a composite volcano blows; mountain a composite volcano blows; mountain collapses inwardcollapses inward

– Example: Crater LakeExample: Crater Lake

c) Cinder Conesc) Cinder Cones

– steep, cone-shaped hills of steep, cone-shaped hills of pyroclastics pyroclastics

– moderately explosivemoderately explosive– most abundant and smallest (<1500 most abundant and smallest (<1500

ft. high)ft. high)– central cratercentral crater– form rapidly, erode rapidlyform rapidly, erode rapidly

example: central Arizona; Paricutin, example: central Arizona; Paricutin, Mexico; Idaho Snake River PlainMexico; Idaho Snake River Plain

Types of volcanism:Types of volcanism:A. ExtrusiveA. Extrusive

1. Volcanoes1. Volcanoes a) shielda) shield b) compositeb) composite c) cinder conec) cinder cone

2. Lava Flows2. Lava Flows flood basaltsflood basalts

B. IntrusiveB. Intrusive

2. Lava Flows2. Lava Flows Effusive (nonviolent) eruptionsEffusive (nonviolent) eruptions spreading boundaries and hot spotsspreading boundaries and hot spots lava spreads out over surface; coming out lava spreads out over surface; coming out

of of fissure fissure (rift)(rift)– example: Lake Superior shore example: Lake Superior shore

1.2 billion yrs BP1.2 billion yrs BP can accumulate layer upon layer : can accumulate layer upon layer : FLOOD FLOOD

BASALTBASALT– examples: Columbia Plateau (Washington), examples: Columbia Plateau (Washington),

Deccan Plateau (India)Deccan Plateau (India)

B. Intrusive VolcanismB. Intrusive Volcanism

Magma solidifies beneath surface; Magma solidifies beneath surface; intrudes into cracks in crustintrudes into cracks in crust

– intrusions can later be exposed at intrusions can later be exposed at surface; more resistant than surface; more resistant than surrounding rocksurrounding rock

Intrusive landformsIntrusive landforms NeckNeck: narrow steep-sided peak , : narrow steep-sided peak ,

formed in central vent of an extinct formed in central vent of an extinct volcanovolcano– E.g., Ship Rock, Devil’s TowerE.g., Ship Rock, Devil’s Tower

DikeDike: thin layer of igneous rock ; : thin layer of igneous rock ; vertical; cuts across other rock layersvertical; cuts across other rock layers

SillSill: thin layer of igneous rock : thin layer of igneous rock between rock layersbetween rock layers

PlutonsPlutons: large igneous bodies at depth: large igneous bodies at depth– batholithsbatholiths– laccolith: dome-shapedlaccolith: dome-shaped