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What can cause some of the most dramatic changes to Earth's surface?

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volcanic Eruptions

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The cause of many volcanic eruptions is the movement of

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earth's tectonic plates

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The movement of tectonic plates is driven by Earth's

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internal heat

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Scientists can learn more about volcanic eruptions by studying

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temperatures within earth

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Combined temperature and pressure in the lower part of the Earth's mantle keeps the rock

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below its melting point

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Despite high temperatures, most of the mantle remains solid because of the

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large amount of pressure from the surrounding rock

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Sometimes Earth's solid mantle and crust melt to form

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magma

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Which of the following is a way that magma can form?

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the temp of the rock in the mantle rises above the melting point of the minerals the rock is composed of

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Magma rises upward through the crust because

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the magma is less dense than the surrounding rock

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As bodies of magma rise toward the surface and melt surrounding rock

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they become larger

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As magma rises and is forced into cracks in the surrounding rock

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large blocks of rock can break off and melt

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Lava flows from an opening in Earth's surface called a

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vent

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Volcanism

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any activity that includes the movement of magma toward or onto earths surface

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Lava

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magma that flows into earths surface; the rocks that forms of when lava cools and solidifies

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Volcanoes erupt on earths surface

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mostly near tectonic plate boundaires

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A major zone of active volcanoes encircling the Pacific Ocean is called the

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pacific ring of fire

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The Pacific Ring of Fire is also one of Earth's major

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earthquake zones

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Many volcanoes are located alone

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subduction zones

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One tectonic plate moves under another in

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a subduction zone

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When a plate of oceanic lithosphere meets a plate of continental lithosphere, the ocean lithosphere

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moves beneath the continental lithosphere

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On the ocean floor, alone the edge of a continent where a plate is subducted,

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a deep trench forms

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At a subduction zone, a plate that consists of continental lithosphere

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buckles and folds to form a line of mountains along the edge of the continent

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As an oceanic plate sinks into the asthenosphere, water can combine with crust and mantle material and

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decrease the melting point of the rock

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When magma rises through the lithosphere to Earth's surface

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volcanic mountains form along the tectonic plate

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When two plates with oceanic lithosphere at their boundaries collide

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one plate subducts, forming a trench

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If a plate with oceanic lithosphere collide with another plate and subducts

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magma forms as fluids are introduced into the mantle

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When oceanic lithosphere subducts beneath the lithosphere, magma rises to the surface to form an

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island arc

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What is an example of the early stages of an Island Arc?

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aleutians islands

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As Island Arcs become larger, they join to form one landmass, such as the islands that make up the

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islands of japan

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Igneous rock

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rock that forms when magma cools within earth

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plutons

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large formations of igneous rock that form as magma cools and solidifies inside the earths crusts

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dikes

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small tubular plutons which may be only a few centimeters wide

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batholiths

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large plutons that cover an area of at least 100km when exposed on earths surface

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Lava provides an opportunity for scientists to study

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the nature of the earths crust and mantle

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By analyzing the composition of volcanic rocks, geologists have concluded that there

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are two general types of magma

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Magma or igneous rock that is rich in feldspars and silica and is generally light in color is

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felsic

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Magma or igneous rock that is rich in magnesium and iron and is generally dark in color is described as

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mafic

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Mafic rock commonly makes up

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oceanic crust

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Felsic rock is common in

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continental crust

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The force of a volcanic eruption is most effected by the

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viscosity of the magma

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Low-viscosity mafic magma results in runny lava and typically causes

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quiet eruptions

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High-viscosity felsic magma results in sticky lava and typically causes

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explosive eruptions

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Explosive eruptions are love likely to be caused by magma with

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large amounts of trapped, aid dolled gases

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Oceanic volcanoes commonly form from

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mafic magma

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Eruptions from oceanic volcanoes are usually

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quiet eruptions

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When mafic lava cools rapidly, it

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forms a crust

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Pahoehoe

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forms a smooth, ropy texture as it cools

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Aa lava

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forms jagged, sharp chunks as it cools

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Blocky lava

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breaks into large chunks at the surface while hot lava continues to flow underneath

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Pyroclastic Material

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consists of fragments of rock that form during a volcanic eruption

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Pyro particles less than 2 mm in diameter are called

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volcanic ash

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Pyro particles less than 0.25 mm in diameter are called

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volcanic dust

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Large clots of red-hot lava that are thrown out of an erupting volcano and then spun through the air as they cool, developing a round or spindle shape are called

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volcano bombs

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The largest pyro particles, which form from solid rock blasted from the cent of a volcano are called

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volcanic blocks

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Volcanic Cone

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structure that is formed from lava and pyro material ejected during a volcanic eruption

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Crater

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funnel shaped put at the top of a volcanic vent

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Shield Volcano

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volcanic cone that is broad at the base and has gently sloping sides

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Cinder Cone

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volcano that isn rarely more than a few hundred meters high and has a steep slope

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Composite Volcano

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volcano that is made from alternating layers of hardened lava flows and pyro material

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Caldera

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large circular depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink

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Important warning signs

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change in earthquake activity around the volcano

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Cause of small earthquakes

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growing pressure on surrounding rock, temperature changes, and fractures, increase in strength from an earthquake

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A problem scientists face when using a volcano's past behavior to predict a future eruption

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few have been studied long enough to establish any activity pattern and volcanoes can suddenly become active after being dormant

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