BellworkCh 18-Volcanic Activity

Compare/Contrast- Types of VolcanoesDirections- Open your binder to the bellwork section

and complete the table. (Textbook p480)Shield Cinder-

ConeComposite

Drawing

Shape Wide, kind of flat

Steep sides, small volcano

Large, wider

Type of Eruptions

quiet More explosive than shield

violent

Low/HighGas content

low Higher than shield

High

Low/High Silica content

low More silica & water than shield

High silica, water

Low/HighViscosity

low Higher than shield

Very high

Ch 18- Volcanic ActivityTake out your notes. As we go over chapter 18, add missing details to

your notes (main idea)

VolcanoA naturally occurring opening in the

surface of the Earth through which molten, gaseous, and solid material is ejected

MAGMAMixture of molten rockSuspended by mineral grainsDissolved gasForms:

High temperaturesPressureWaterSource material

TYPES OF MAGMA

Basaltic

Basalt igneous rock

Ex: Hawaiian Islands

Andesitic

Andesite igneous rock

Ex: Mt. Saint Helens / Tambora

Rhyolitic

Granite igneous rock

Ex: Yellowstone Nat’l Park

What is viscosity?Property of

fluid that resists flowing

The hotter the magma or lava, the lower the viscosity.

MAGMA COMPOSITION & CHARACTERISTICS

HOW MAGMA AFFECTS THE CRUSTBLOCKS TO BREAK OFF AND SINK

MELTS OTHER ROCKSROCKS TO FRACTURE

PLUTONS When magma cools, minerals form. Over a very long period of time,

these minerals will combine to form intrusive igneous rock bodies called plutons.

Largest plutons are called batholiths. Common in the interiors of major mountain chains. – primarily granite

Irregular shaped plutons are called stocks.

Mushroom-shaped pluton is called a laccoliths.

Sills – pluton intrudes parallel to layer rocks.

Dikes cuts across preexisting rocks.Coast Range Batholith in British Columbia

PLUTONS

Parts of a Volcano

VENT- the vent is the opening from which lava flows. Dust, ash, and rock particles can also be thrown out of the vent!

Crater- the top of the volcano. It is a funnel shaped pit. It is formed when the material explodes out of the vent!

Volcanic cone-is the pile oflava, dust, ashes,and rock aroundthe vent. It canbe found in different shapes!

3 Types of Volcanoes

Shield Cinder Cone Composite

They are classified by how they form.

Shield Volcano Is wide and

somewhat flat. It forms from a

quiet eruption. Lava flows out

quietly and for great distances.

Cinder Cone Volcano Has tall, very

steep sides. Has explosive

eruptions. This eruption

produces a lot of cinder and ash.

Composite Volcano Form from

explosive eruptions.

Produce a lot of lava and ash.

Is small, with steep sides.

Tephra Rock fragments, classified by size,

that are thrown into the air during a volcanic eruption and fall to the ground.

Pyroclastic flow Swift-moving, potentially deadly

clouds of gas, ash, and other volcanic material produced by a violent eruption.

Hot Spot

Unusually hot area in Earth’s mantle that is stationary for long periods of time, where high-temperature plumes of mantle material rise toward the surface.

Where do volcanoes occur?

Active volcanoes generally occur close to the major tectonic plate boundaries. Along convergent and divergent plate boundaries.

They also form over hot spots – hot areas in the mantle

Volcanoes can remain inactive, or dormant, for hundreds or thousands of years before erupting again. During this time they can become covered by vegetation making them difficult to identify. Once a volcano has been dormant for more than 10,000 years, it is termed extinct.

Test- Plate Tectonics/Volcanoes

Next Class!! Frida

* Be sure to study from the study guides, notes, bell work, class work and homework.

Classwork/AssignmentTextbook/Review for exam

1. Problem-Solving Lab- Textbook page 486 Analysis Qs 1,2/ Think Critically Qs 3,4

2. Page 447 Compare/Contrast #63. Page 454 Concept Mapping # 64. Page 459 Making Tables # 65. Page 475 Concept Mapping # 7You may work with a partner- All work is

due in basket at the end of class!!!