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Volcanoes - 6th Grade

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William Begoyan

on 3 October 2017

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Transcript of Volcanoes - 6th Grade

Volcanoes
Page 15 in ISN
(pages 210-245 in your textbook)

AVID EQ: How are
volcanoes made?
Volcano
A
volcano
is a weak point in the crust where molten material can rise to the surface.
Magma
is a molten mixture of rock, gas, and water from the mantle.
Magma
that reaches the surface is called
lava
.
Ring of Fire
There are about 600 active volcanoes in the world, and most are near boundaries of tectonic plates.
Most are found under water.
About 450 of all active volcanoes are found in a volcanic belt called the
"Ring of Fire".
Boundaries and Volcanoes
Volcanoes can form near the rift valleys of two separating plates.
Volcanoes also form near continental/oceanic subduction zones.
Island Arcs
When any oceanic plate subducts under another away from the coastline, an
Island Arc is
formed.
The Japanese islands are an example of this.
Hot Spot Volcanoes
At times, a
hot spot
in the mantle can burst through the crust at
non-boundaries
.
A volcano will form at that location.
The Hawaiian Islands are formed in this manner.
Volcanic Eruptions
Volcano Structure
Magma chamber
:
located under the volcano, magma collects here.
Pipe:

a long tube that connects the magma chamber to the surface.
Vent:

an opening through which magma and gas exit the volcano.
Lava Flow:

part of the volcano that is covered by lava.
Crater:

a bowl shaped area that can form at the top of the volcano around the central vent.
There are two major types of eruptions,
quiet
and
explosive
.
The amount of silica material present in the magma determines which type you have.
Low silica
content yields quieter eruptions,
high silica
content yields explosive eruptions.
Low silica magma is thinner and can ooze out easier out of the volcano.
High silica magma is thick, and will get stuck. It will build up until it violently explodes out.
Explosive eruptions always include
pyroclastic flows
, a mixture of hot gases, ash, and cinders.
What is a volcano?
What is the difference between magma and lava?
What is magma made of?
Where can we find the majority of volcanoes on Earth?
Is there a relationship between boundaries and volcanoes?
What is an Island Arc?
What is a hot spot volcano?
Stages of Volcanoes
A
dormant
volcano is not currently erupting, but can become active in the future.
Active
volcanoes are either erupting or will erupt in the near future.
An
extinct
volcano is dead, not likely to erupt ever again.
Types of Volcanoes
Shield Volcanoes
have gentle slopes with gradual lava flows. They aren't explosive due to low silica magma.
Composite Volcanoes

have steeper slopes then shield volcanoes. Due to the higher silica content, composite volcanoes can be partially explosive.
Cinder Cone Volcanoes
have the steepest slopes of the three. Due to the very high silica content, they are the most explosive volcano types.
Hot springs
are found near areas of current or past volcanic activity. Water is heated by nearby magma or hot rock.
When magma heated water is trapped, it will eventually escape as a
geyser.
Magma Landforms
2. Dike:

Magma forces itself across rocks vertically (up/down), which later cools.
Magma that fails to reach the surface (but gets close) can form the following 3 features.
1. Sill:

Magma forces itself across rocks horizontally (sideways), which later cools.
3. Laccolith:
Magma forces itself into rocks and pools there, which later cools.
i
What is a magma chamber?
What is a vent?
What is a pipe?
What is a crater?
What are the two types of eruptions, and what do they depend on?
What are the three types of volcanoes?
What is different between the 3 types of volcanoes?
How are hot springs and geysers formed?
What is sill?
What is a dike?
What is a laccolith?
Homework
On page 14 draw and label all of the parts of a volcano (magma chamber, pipe, vent, crater, lava flow, sill, dike, laccolith).
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