Download Volcano and Geologic Time Summary Sheet

Volcano Summary Sheet
1. volcano: a cone-shaped mountain where magma, solids, and
gases are released
2. magma: molten rock found inside the Earth
3. lava: molten rock found on the Earth’s surface
4. viscosity: thickness of lava
a. depends on the amount of silica
b. the more silica, the thicker the lava is
5. How do volcanoes form?
a. Form at subduction zones (convergent boundaries)  the
more dense, oceanic plate sinks under the less dense
plate
b. The plate reaches deep within the Earth and begins to
melt because of high temperatures
c. The magma collects and makes its way to the Earth’s
surface
d. Once it reaches the surface it will create a volcano
6. Parts of a volcano  Please see vocabulary sheet handed out
in class
7. Types of volcanoes
a. Shield volcano
i. Wide base with gentle sloping sides
ii. Quiet eruptions
1. Creates lava flows
iii. Low viscosity, lava is runny
iv. Example: Mauna Loa and Mt. Kilauea in Hawaii
b. Cinder cone volcano
i. Narrow (thin) base with steep sides
ii. Explosive eruptions
1. Large amounts of gas, cinders, and dust from
volcano
iii. Higher viscosity, lava is generally thicker
iv. Example: Mt. Paricutin in Mexico
c. Composite (Stratovolcano) volcano
i. Wide base with steep sides
ii. Quiet and explosive eruptions
1. Creates alternating layers of lava and gas,
cinders and dust
iii. Example: Mt. St. Helens in Washington, USA
8. active volcano: currently erupting or has in the recent past
9. dormant volcano: “sleeping”  has not erupted in many
years but has a magma chamber
10. extinct volcano: will not erupt because it does not have a
magma chamber
11. Ring of Fire
a. 80% of all earthquakes and volcanoes occur here
b. Located around the Pacific Ocean (Pacific Plate)
Geologic Time Summary Sheet
1. Geologic Time Scale: a chart used to show great changes in
biodiversity throughout Earth’s history
2. Know how to read the Geologic Time Scale
a. Most recent time  at the top
b. Separated into Eons, Eras, Periods, and Epochs
i. Similar to a classification chart, it gets more specific
toward the Epochs
ii. Eons  longest period of time
3. Law of Superposition: new layers of rock are built over
older layers of rock
a. Older rock layers  towards bottom of the crust
b. New rock layers  at top of crust
4. Absolute age: actual age of rock depending on chemical
make-up
5. Relative age: age of rock compared to objects around it
(estimate)
6. Radiometric dating: the process of calculating the absolute
age of a rock
7. Review Geologic Time Vocabulary