Geology ~ Chapter 2 & 12

Shield Volcano

-A broad, gently sloping volcano built from fluid basaltic lavas. - A broad, shield-shaped volcano many tens of kilometers in circumference and more than 2 km high, built by successive flows of basaltic lava from a central vent.

Mantle Plume

-A column of very hot rock rising up through the mantle. - A narrow, cylindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism

Plate Tectonics

-Earth's crust is a jigsaw puzzle of about 13 distinct plates - The theory that describes and explains the creation and destruction of Earth's listhospheric plates and their movement over earth's surface

Alfred Wegener

-Published theory of continental drift in 1915 -"The Origin of Continents and Oceans" -Initially rejected *Reason for how plates moved was proved wrong

Hot Spot

-Region of intense, localized volcanism found far from a plate boundary, hypothesized to be the surface expression if a mantle plume -An area of volcanic activity, especially where this is isolated.

Continental Drift

-Simple idea that continents seem to fit together and therefore must have "drifted" apart -Key Technology: SONAR - The large-scale movements of continents across Earth's surface driven by the plate tectonic system

Asthenosphere

-The soft layer of the mantle on which the lithosphere floats/ plates move. -the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

Diatreme

-a long, vertical pipe or plug formed when gas-filled magma forced its way up through overlying strata -form when a volcanic vent and the feeder channel below it are left full of bracchia as an explosive eruption wanes.

What are super volcanoes? How dangerous is Yellowstone?

-resurgent caldera -more than 250 cubic miles of magma erupted -very explosive -highly viscous - Yellowstone is dangerous because massive resolvers of super viscous lava magma Build-up over a long period of time. Gasses are easily trapped under rhyolitic lavas and large rhyolitic volcanoes such as Yellowstone, produce the most explosive explosive of all volcanic eruptions. -an unusually large volcano having the potential to produce an eruption with major effects on the global climate and ecosystem -Very dangerous -Would cover half of US and 3ft of ash -Global climate change -Nuclear winter for years

Volcanic Dome

-roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. -usually produced by andesitic and rhyolitic lavas

Seafloor Spreading

-the formation of new areas of oceanic crust, which occurs through the upwelling of magma at midocean ridges and its subsequent outward movement on either side. -Explains how continents move.

Crater

1. A bowl-shaped pit found at the summit of the most volcanoes, centered on the vent 2. A depression caused by the impact of a meteorite

Types of Convergent Boundaries

1. Ocean-Ocean: melting of mantle material creates volcanoes. 2. Ocean-Continent: Earthquakes and volcanoes, mountain range-continental arc 3. Continent-Continent: Too buoyant to subduct, will smash together and push up creating mountains and earthquakes.

Key Evidence for Seaflooor Spreading

1. Topography of ocean floor 2. Combined with worldwide earthquake information

What were the key pieces of evidence that led to the development of the theory of plate tectonics over time?

1. Topography of ocean floor 2. Combined with worldwide earthquake information

Approximately what percentage of Earth's active volcanoes occurs at convergent plate boundaries?

80%

Which of the following volcanoes is not a composite volcano (stratovolcano)? A. Mauna Loa, Hawaii B. Mt. Rainier, Washington C. Fujiyama, Japan

A

Divergent Boundary

A boundary between lithospheric plates were two plates move apart and new lithosphere is created

Convergent Boundary

A boundary between lithospheric plates where the plates move toward each other and one plate is recycled into the mantle. THe denser plate, oceanic, is subducted underneath the less dense plate, which can be either continental or oceanic.

Island Arc

A chain of volcanic islands formed on the overriding plate at a convergent boundary by magma that rises from the mantle as water released from the subducting lithosphere it slap causes fluid induced melting.

Stratovolcano

A concave-shaped volcano formed from altering layers of lava flows and beds of pyroclasts.

Basalt

A dark, fine-grain, mafic igneous rock composed largely of plagioclase feldspar and pyroxene; the extrusive equivalent of gabbro.

Pyroclastic Flow

A glowing cloud of hot ash, dust, and gasses injected by a volcanic eruption that rolls downhill at high speeds.

Almost all of the 25000 people killed in the 1985 eruption of Nevada del Ruiz in Colombia were killed by ______.

A large mudflow of volcanic debris/lahar

Caldera

A large, steep-walled, basin-shaped depression formed by violent volcanic eruption in which large volumes of magma are discharge rapidly from a large magma chamber, causing the overlying volcanic structure to collapse catastrophically through the roof of the empty chamber.

Transform Boundary

A plate boundary at which the plates slide horizontally past each other and lithosphere is neither created nor destroyed.

Pyroclasts

A rock fragment ejected into the air by a volcanic eruption.

Pangeae

A supercontentinent that coalesced in the late Paleozoic era and comprised all present continents, then began to break up in the Mesozoic era.

Lahar

A torrential mudflow of wet volcanic debris

How and when did the idea of Continental Drift develop?

Alfred Wegner 1912 later 1915 when he published the book

Fissure Eruption

An eruption in which lava is extruded from narrow vertical fractures or cracks in the crust, rather than a central vent

Large Igneous Province

An extremely large accumulation of igneous rocks, including plutonic rocks or volcanic rock formations, arising when hot magma extrudes from inside the Earth and flows out.

Flood Basalt

An immense basalt plateau formed by fissure eruptions of highly fluid basaltic lava.

Which of the following mountain chains is made up of primarily of volcanoes formed at an ocean- Continent subduction zone?

Andes

Find the correct volcano/volcanic product match. A. dome/basalt B. shield volcano/rhyolite C. fissure/basalt D. shield volcano/andesite

B

Which of the following lavas will flow downhill slowest? A. andesite B. basalt C. rhyolite D. same speed for all

C

which of the following structures/materials does NOT erupt from a single central vent? A. cinder cones B. composite volcanoes C. flood basalts

C

A _______ is a large, steep-walled, basin-shaped depression formed by a violent volcanic eruption I which large volumes of magma are discharged rapidly from a large magma chamber, Cathay the overlying volcanic structure to collapse catastrophically through the roof of the emptied chamber

Caldera

The cascade volcanoes are associated with a ________.

Convergent plate margin

What type of rock makes up the Columbia plateau of Oregon and Washington?

Flood basalts

What was the initial evidence for continental drift?

Geologic similarities, the continents bordering the Atlantic seemed to fit together like a jigsaw puzzle.

How do we measure plate motion today?

Global Positioning System (GPS)

How and when did the idea of Sea-Floor spreading develop?

In the 1960's, Harry Hess proposed that Earth's crust separates along the rifts in the mid ocean ridges, and the new crust was formed by the upwelling of hot molten rock into these cracks.

How was the Columbia Plateau formed?

It formed between 6 million and 16 million years ago as the result of successive flows of basalt.

What is the name of the tectonic plate that is currently under us?

Juan de Fuca

What volcanic hazard is considered the most dangerous in the Cascade Range?

Lahars

The laki eruption of 1783 in Iceland is considered the ______ in recorded history.

Largest outpouring of lava

Which of the following statements about the viscosity of lovers is true?

Lava viscosity increases as the silica content of the lava increases

What is molten rock beneath the Earth's surface called?

Magma

Phreatic Eruption

Magma inside volcanoes come into contact with a lot of water, causing a steam explosion

Which hypothesis proposes that large igneous provinces for my hotspots by mantle plumes at originate at the boundary within the Earth?

Mantle-outer core boundary

The 2004 eruptive activity on mount Saint helens was what type of eruptive activity?

Medium viscosity lava flow

Where does most volcanic activity on the sea floor take place?

Mid-ocean ridges

How does plate tectonics theory account for the distribution of most of the world's volcanoes, earthquakes, young mountain ranges, and major sea-floor spreading?

Most earthquakes, volcanoes and islands are located at the boundaries of tectonic plates. -Mountain Ranges and Major Earthquakes -Ring of Fire

What is the general pattern of earthquakes around the world? How is it related to plate tectonics?

Mostly occur at plate tectonic boundaries

Which of the following volcanoes is a composite volcano (stratovolcano)?

Mt. Rainier, Washington

Magnetic Anomaly

One in a pattern of a long, narrow bands of high or low magnetic intensity on the sea floor that are parallel to and almost perfectly symmetrical with respect to the crest of a mid ocean ridge.

What is the name for a basaltic lava flow that has a ropy, folded surface?

Pahoehoe

Over the last 2000 years, which of the following volcanic hazards has cost the most fatalities?

Pyroclastic flows

Why is Rainier considered the more dangerous volcano than St. Helens?

Rauner has more glacial ice

Viscosity

Resistance to flow; viscous=safe

How has plate motion been tested by studying marine magnetic anomalies?

SONAR????

What are the key differences between shield volcanoes, cinder cones, and stratovolcanoes?

Shield Volcanoes: -largest -made of lava flows -erupts consistently for millions of years Cinder Cones: -smallest -made of pyroclasts -short, single eruptive event (never again) Stratovolcano: -intermediate -made of pyroclast and lava flows -periodic explosive eruptions as well as medium viscosity lava growth events

Volcanic rocks derived from the Yellowstone hotspot get progressively older to the Southwest. Based on this information, in which direction is the North American plate moving?

Southwest

What Cascade Range volcano has been the most active in the last 4000 years?

St. Helens

What cascade range will taint Volcano has been the most active in the last 4000 years?

St. Helens

What type of a canek gasses form aerosols in the upper atmosphere that can cause global cooling?

Sulfur dioxide

How are volcanoes associated with plate boundaries?

The Earth's most active volcanoes occurred and a convergent plate boundaries. 80% at convergent plate boundaries, 15 at Divergent plate boundaries, 5 in intraplate.

Most of the world's active volcanoes are located her on the edge of which ocean?

The Pacific Ocean

In the basalt sample depicted below, the vesicles (small spiracle cavities) were most likely formed by ______.

The escape of gas bubbles dissolved in the lava during the eruption

Magnetic Field

The region of influence of a magnetized body or an electric current.

Subduction

The sinking of oceanic lithosphere beneath overriding oceanic or continental lithosphere at a convergent plate boundary

Lithosphere

The strong, rigid outer shell of Earth that compromises the crust and the uppermost part of the mantle down to an average depth of 100 km (litho=stone)

How often do Cascade Range volcanoes explosively erupt?

Twice every 100 years

What type of eruptive activity form the Colombia Plateau?

Very low viscosity lava flows

How can mechanic your options in danger commercial air traffic?

Volcanic ash lofted into the air can damage engines.

How are the Hawaiian islands forming?

Volcanoes can form in the Middle of the plate, where magma restless upward until it erupts on the sea floor, at what is called a hotspot. The Hawaiian Islands were formed by such a hotspot occurring in the middle of the Pacific plate. The movement of a plate over a hotspot generates a trail of progressively older volcanoes. The volcanoes of the Hawaiian island chain and its extension into the Northwestern Pacific show in Northwest trend toward progressively older ages.

Why was continental drift initially rejected?

Wegener didn't have any strong evidence to support his theory. He suggested that the gravitational pull of the moon and planet moved the continents.

What type of a canek flows likely formed a volcano depicted in the cross-section below?

basalt flows

Mantle plumes are thought to originate at the ____ boundary.

core-mantle

What sort of Volcano was formed during the laki eruption Iceland in 1783?

fissure

An eruption of lava that pours out of a vertical cracks along the flank of a Kanal are referred to as _______ ________.

fissure eruption

An eruption of lava with a pours out of a vertical cracks along the flank of a volcano referred to as a _______ ________.

fissure eruption

The landscape of much of Eastern Washington was formed by a ______, which is an immense bsalt plateau formed by fissure eruptions of highly fluid basaltic lava.

flood basalt

Cinder-cone Volcano

forms when material ejected high into the air falls back to Earth and piles up around the vent

Old faithful Inn jealous own National Park is an example of a ______.

geyser

Why is Rainier the most dangerous volcano in America?

glacial ice

Mantle Convection

heat needs to escape (rise up)

What are the different types of eruptive activities that stratovolcanoes exhibit?

lava flows and pyroclastic deposits

What are the major volcanic hazards and their relative dangers?

lava flows, lahars, ash falls, debris avalanches, pyroclastic density currents (flow). lava dome, collapse and pyroclastic flow eruption cloud fumaroles landslide ash fall bombs acid rain tsunamis

Magma generated in Earth's core interior rises because it is ____ _____ than the surrounding rocks.

less dense

A ______ _____ is a narrow, cylindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism. It causes hotspots and flood basalts.

mantle plume

The eruption of vast quantities of superheated steam is called a ________ _________.

pheartic explosion

A ___________ ____ is a deadly cloud of hot ash, dust, and guesses ejected by a volcanic eruption that rolls downhill at high speeds.

pyroclastic flow

Solidified fragments of volcanic material ejected into the air are called __________.

pyroclasts

Yellowstone, in Wyoming, is an example of a _____ _______.

super volcano or caldera

Why do the plates move? What drives plate tectonics?

the heating of the mantle by comvection

On average how often new cascade range volcanoes explosively erupt over a 100 year time period?

two

What are the major features associated with diverging, converging and transform plate boundaries?

volcanoes, islands and earthquakes