Magma
Molten mixture of rock-forming substances, gases, and water
from the mantle....in a liquid form
LAVA
Magma that reaches the surface
When Lava cools, it forms solid rock
Lava released during volcanic activity builds up Earth’s surface
What is the difference?
When this type of lava cools, it forms the rock rhyolite, which has
the same composition as granite.
Volcano
A weak spot in the crust where magma has come to the surface.
Hot Spot Volcanoes
An area where magma from deep within the mantle melts
through the crust above it.
A volcano forms above a hot spot when magma erupts through
the crust and reaches the surface.
Volcanoes
Ring of Fire
Hawaii
Island Arc
A string of islands formed by the volcanoes along a deep-ocean
trench.
Volcanos form at:
Divergent Plate Boundaries
- Lava can spill out at Mid Ocean Ridges and form mini mountains
Convergent Boundaries
- The rock above the subducting plate melts and forms magma.
Magma rises toward the surface and breaks through the ocean
floor, creating volcanoes.
How Fast?
Measured from the bottom of the Pacific Ocean, the Big Island of
Hawaii is the largest mountain on Earth. The island is made up of
massive volcanoes. One of these volcanoes, Mount Kilauea (kee
loo ay uh) erupts frequently and produces huge amounts of lava.
At a temperature of around 1,000°C, lava from Mount Kilauea is
very dangerous. Yet most of the time, the lava moves slower than
a person can walk—about 1 kilometer per hour. Some types of
lava move much more slowly—less than the length of a football
field in an entire day.
Properties of MAGMA
Physical Properties
What is a physical property?
700-1300 degrees Celcius
Bright Red, Black, Orange, Yellow
Chemical Properties
What is a chemical property?
Chemical Composition
Made up of at least 10 elements
Silicon(Si), Titanium (Ti), Aluminum (Al), Iron (Fe), Magnesium
(Mg), Calcium (Ca), Sodium (Na), Potassium
(K), Hydrogen (H) and Oxygen (O).
Amount of Heat
Viscosity
The resistance of a liquid to flowing.
Because liquids differ in viscosity, some liquids flow more easily
than others.
Silica (Silicon and Oxygen) determine viscosity
More Silica= greater viscosity
produces light colored lava
A decrease in temperature increases viscosity
Shield Volcanoes
A wide, gently sloping mountain made of layers of lava and
formed by quiet eruptions.
Cinder Cone Volcano
A steep, cone-shaped hill or small mountain made of volcanic
ash, cinders, and bombs piled up around a volcano’s opening
Composite (Stratovolcano)
A tall cone-shaped mountain in which layers of lava alternate
with layers of ash and other volcanic materials.
Quiet Eruptions
magma is low in silica
gases in magma bubble gently
lava oozes quietly and can flow for many kilometers
build up islands over hundreds and thousands of years
for example, the Hawaiian islands
Explosive Eruptions
magma is high in silica
magma does not always flow out of the crater
gets stuck/plugs up volcano
the gases from the magma create pressure and eventually erupt!
Low Silica
Quiet Eruptions
Low viscosity
Easy flow
High Silica
Explosive Eruption
High Viscosity
Thick and Sticky
The color of lava depends on its temperature.
Bright Orange
--> 1000-1150 C
Bright Red
--> 800-1000 C
Dark Red
--> 650-800 C
Brownish Red
--> 500-650 C
Black
--> solid lava/rock (but can still be very hot).
Lava Color
Stages of Volcanoes
1) Active
-erupting or has shown signs that it may erupt in the near future
2)Dormant
-A volcano that is not currently active, but may become active in
the future.
3) Inactive
-dead, unlikely to erupt again