Explosive Eruption

Volcano Vocabulary

VOLCANISM

VENT

CRATER

CALDERA

QUIET ERUPTION

EXPLOSIVE ERUPTION

PYROCLASTIC DEBRIS

CINDER CONE

SHIELD VOLCANO

COMPOSITE VOLCANO

STRATO VOLCANO

ACTIVE

DORMANT

EXTINCT

INTRUSION

DIKE

SILL

LACCOLITH

PLUTON

BATHOLITH

STOCK

ROCK CYCLE

Igneous

REMELTED REMELTED

BURIED BURIED

HEAT ERODED

PRESSURETRANSPORTED

DEPOSITED

Metamorphic Sedimentary

ERODED, TRANSPORTED

DEPOSITED

HEAT

PRESSURE

I.Heat within the Earth

A. For every ______we go beneath the surface the temperature increases ______degrees Celsius.

B. Sources of heat:

1. ______decay- like a thermonuclear reactor is partly responsible for heat within the Earth. Atoms are splitting apart or decaying.

Original ______- Crust has insulated the heat trapped within since the Earth's formation about 5 ______years ago.

3. ______- Tremendous heat created from the convection currents within the ______.

II.Magma (molten rock ______the surface that is

mostly silica)

A. Formation

1. Molten rock within the Earth is called ______. Molten rock extruded onto the surface is called ______. Magma forms at a depth of about 40 to 60 kilometers. Magma ______ have a temperature of 650 to 1500 degrees Celsius- or about 1,200 to 3,000 degrees Fahrenheit.

B. Types/ Chemical Composition of Magma

______- Also known as Pahoehoe, Mafic and Oceanic.

Contains less percentages of silica (SiO2) and more Magnesium oxide (MgO). It has a very thin, runny texture or ______viscosity.

Temperature of Mafic lava ranges between 1000 and 1500 degrees Celsius. High relative ______.

2. ______- Also known as aa, Felsic and Continental. Contains more silica (SiO2) and Aluminum oxide (Al2O3).

It has a ______and pasty texture or high viscosity.

Temperature of Felsic lava is about 650 to 950 degrees Celsius.

______relative density.

Magma Type:FELSIC INTERMEDIATE MAFIC

75% SiO<------<------<------<------45% SiO2

increasing percentage of silica

<------<------<------<------

increasing Na2O & K2O

------>------>------>------>

increasing CaO, FeO, & MgO

Common Rock: RHYOLITE ANDESITE BASALT

GRANITE GABBRO

III. Anatomy of a Volcano

A. Common Features

______Chamber- as magma rises to the surface it forms a large pocket beneath the surface that holds the magma.

AKA: ______, Batholith, Stock

______- is a narrow crack in the crust or bedrock through which magma flows.

______- central opening that allows the magma to flow to surface. Where magma leaves the pipe.

______- the basin or bowl-like depression over the vent at the ______of the cone.

IV. Kinds of Eruptions

A. ______ Eruption

Typical of the Basaltic/Mafic/Oceanic______flow.

A "fissure flow" describes lava running out onto the surface in wide, thin sheets. Often these sheets form a ropy surface called ______- which means "satin-like".

These flows can lead to a topography called a ______Plateau.

Mauna Loa (Hawaii) is a good example of a series of quietly erupting lava.

B. ______ Eruption

1. Typical of the ______/Felsic/Continental lava flow.

When lava of this type erupts, a great deal of gas and ash erupt with it. The appearance of this kind of lava is sharp and jagged which led to its name- ______. The particulate matter that explodes from the volcano is called Pyroclastic Debris.

Pyroclastic Debris (AKA: ______) is categorized by size:

~Smallest is called Tuff or ______

~Sand-sized particles are called ______

~Pebble-sized particles are called ______

~Cobble to truck-sized called Volcanic ______

V. Types of Volcanoes

A. Classification

Volcanic classification is determined by composition & ______.

The ______ determines chemistry of magma/lava and consequently the type of eruption as well. The material ejected from the volcano and deposited around the vent produces the ______.

B. Types

1. ______- is a small, steep-sided volcano made mostly of cinders & tuff (tephra), often with lava flows intermixed.

The height is usually less than ______feet (200 meters). The Cinder Cone tends to erode quickly and may bleed from the bottom or sides- called a "______eruption". These volcanoes ______often cause damage in that they are small, intermittent explosions of Felsic lava.

Examples are ______(Crater Lake) and Paricutin (1943, Mexico).

2. ______Volcano- is usually wider than it is tall, much like a shield. It is almost entirely made of mafic lava (______).

The Shield has a 2 to 10 degree slope and most often found near ______or on oceanic crust. The lava flow itself can cause significant damage though its eruptions are tectonically quiet.

An example is Mauna Loa (Hawaii)

______Volcano- is similar in structure and composition to Shield Volcanoes. In this type of structure, huge quantities of lava exude onto the surface from fissures in the crust. These volcanoes are very difficult to identify yet are very common. Sheet Volcanoes are the largest volcanoes in area, often covering thousands of square kilometers.

An example is the Columbia Plateau (Washington & Oregon).

3.Composite or ______Volcano- is a large, steep-sided volcano made of alternating layers of lava flow and pyroclastic debris. Its structure and behavior is highly complex. Strato Volcanoes are considered to be extremely ______due to their inconsistent behavior. These volcanoes are extremely explosive at times, while at other times the eruptions are quiet. The nature of the eruption is determined by the ______location.

______of Composite Volcanoes are Mount St. Helens (Washington), Mount Vesuvius (Mediterranean), and Mount Pinatubu (Philippines) which exploded in June of 1991.

a. The ______, or nuees ardentes, is the main killer in ______eruptions. The superheated gas rushes down the cone in excess of ______miles per hour and often exceeds temperatures of 800 degrees Celsius or 1,500 degrees Farenheit. On May 8, 1902 Mont Pele’e erupted on the Caribbean island of Martinique. A nuees ardentes blew down the slope at over 700 degrees Celsius killing ______people in the city of St. Pierre within only two minutes. Only ______people are known to have survived.

______- a volcanic depression much larger than the original crater. It is either an exploded volcano or a ______volcano.

Examples are Krakatoa (Indonesia) Crater Lake (Oregon), and Mount St. Helens after 1980 (Washington).

VI. ______of Volcanoes

1. ______Volcano- is a volcano that is erupting now, has erupted in the recent past, or shows signs of erupting in the near future.

2. ______Volcano- is a volcano that has not erupted recently, but has during recorded history. It is expected to erupt again in the future.

3. ______Volcano- is one that has not erupted in recorded history. It is unlikely to erupt again.

VII. Volcanism Underground

______- are flows of magma that cool and harden before they reach the surface. Intrusive igneous rocks have a large grain, or crystal, size.

The the intrusion, the the grain size

1. Volcanic ______- is an intrusive structure composed of cooled magma trapped in the throat or vent of a volcano.

2. ______- is a tabular, typically ______intrusion (discordant).

Dikes formed at ______depths can have ______grained texture, while those at greater depths may have a coarse grained texture. Often dikes will be ______resistant to erosion and leave a wall-like protrusion on the surface. An example is Ship Rock (New Mexico). There also dikes in Wisconsin.

3. ______- is a relatively horizontal structure that is parallel (cordant) to the layers of country rock. Magma squeezes ______sedimentary rock and solidifies into a sill. Like dikes, the grain texture of a sill is dependant upon ______.

4. ______- is a close relative of the sill which often leaves a bulge at the surface. It has a slight dome or ______shape, with the middle of the structure being thicker than the sides. These can form smaller dome mountains.

5. ______- is an igneous body that has cooled and crystallized at great depths. Plutons have irregular shapes and often cause ______of bedrock at the surface.

a. ______- is a small discordant (nearly vertical) pluton with an outcrop area of ______than 100 square kilometers.

b. ______- is a large discordant pluton with an outcrop area of ______than 100 square kilometers. Most batholiths are felsic in composition, being mostly granite.

Written and compiled by

Peter J. Watts

Riverside Middle School

131 Hall Street

Watertown, WI 53094