Volcanoes- 13.1 and 13.2

What can cause some of the most dramatic changes to Earth’s surface?
volcanic Eruptions

The cause of many volcanic eruptions is the movement of
earth’s tectonic plates

The movement of tectonic plates is driven by Earth’s
internal heat

Scientists can learn more about volcanic eruptions by studying
temperatures within earth

Combined temperature and pressure in the lower part of the Earth’s mantle keeps the rock
below its melting point

Despite high temperatures, most of the mantle remains solid because of the
large amount of pressure from the surrounding rock

Sometimes Earth’s solid mantle and crust melt to form

Which of the following is a way that magma can form?
the temp of the rock in the mantle rises above the melting point of the minerals the rock is composed of

Magma rises upward through the crust because
the magma is less dense than the surrounding rock

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

As magma rises and is forced into cracks in the surrounding rock
large blocks of rock can break off and melt

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

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

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

Volcanoes erupt on earths surface
mostly near tectonic plate boundaires

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

The Pacific Ring of Fire is also one of Earth’s major
earthquake zones

Many volcanoes are located alone
subduction zones

One tectonic plate moves under another in
a subduction zone

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

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

At a subduction zone, a plate that consists of continental lithosphere
buckles and folds to form a line of mountains along the edge of the continent

As an oceanic plate sinks into the asthenosphere, water can combine with crust and mantle material and
decrease the melting point of the rock

When magma rises through the lithosphere to Earth’s surface
volcanic mountains form along the tectonic plate

When two plates with oceanic lithosphere at their boundaries collide
one plate subducts, forming a trench

If a plate with oceanic lithosphere collide with another plate and subducts
magma forms as fluids are introduced into the mantle

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

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

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

Igneous rock
rock that forms when magma cools within earth

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

small tubular plutons which may be only a few centimeters wide

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

Lava provides an opportunity for scientists to study
the nature of the earths crust and mantle

By analyzing the composition of volcanic rocks, geologists have concluded that there
are two general types of magma

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

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

Mafic rock commonly makes up
oceanic crust

Felsic rock is common in
continental crust

The force of a volcanic eruption is most effected by the
viscosity of the magma

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

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

Explosive eruptions are love likely to be caused by magma with
large amounts of trapped, aid dolled gases

Oceanic volcanoes commonly form from
mafic magma

Eruptions from oceanic volcanoes are usually
quiet eruptions

When mafic lava cools rapidly, it
forms a crust

forms a smooth, ropy texture as it cools

Aa lava
forms jagged, sharp chunks as it cools

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

Pyroclastic Material
consists of fragments of rock that form during a volcanic eruption

Pyro particles less than 2 mm in diameter are called
volcanic ash

Pyro particles less than 0.25 mm in diameter are called
volcanic dust

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
volcano bombs

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

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

funnel shaped put at the top of a volcanic vent

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

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

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

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

Important warning signs
change in earthquake activity around the volcano

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

A problem scientists face when using a volcano’s past behavior to predict a future eruption
few have been studied long enough to establish any activity pattern and volcanoes can suddenly become active after being dormant

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