Name ____________________________ Class: _______ TEST DATE: Wednesday February 24
Chapter 7 Study Guide: Volcanoes
1. Define intrusive features.
- When magma cools underground, it forms intrusive features, that later can
be exposed by erosion (by wind or water).
2. Differentiate between intrusive and extrusive igneous rock formation.
- Intrusive: magma cools underground—exposed later.
-
Extrusive: form from past and current volcanic eruptions—form on the
outside of the surface.
3. Sticky, thicker lava is rich in _SILICA_
4. What is the difference between magma and lava?
-
Magma: molten rock on the inside of a volcano/underneath Earth’s surface.
Lava: molten rock on the outside of Earth’s surface.
5. Give 5 facts about shield volcanoes.
- Huge and gently sloping sides.
Composed of layers of basaltic lava, that form over time.
- It has quiet explosions.
- Some of these mountains/volcanoes reach altitudes of more than 2400
meters.
- They resemble the shape of a warrior’s shield.
-
6. Give 5 facts about cinder cone volcanoes.
-
Cone shaped and steep sided
Composed of basaltic lava.
Mainly composed of/developed from solid fragments of tephra
Produce Explosive eruptions.
They do not represent all possible types of eruptions.
7. Give 5 facts about composite volcanoes.
-
Tall majestic mountains
Composed of basaltic and granitic lava
They develop by alternating layers of lava and tephra
The eruptions are both explosive and quiet
Altitudes of more than 2438 meters.
They occur at convergent plate boundaries and form tall mountains.
8. Give 4-5 facts about basaltic lava.
-
Thin and runny
Erupts quietly
Flows freely
High heat
Low silica
Low viscosity
9. Give 4-5 facts about granitic lava.
- High viscosity
-
Thick, lumpy, sticky
Erupts explosively
Low heat
high silica
Flows slowly
10. How and why does magma rise toward the surface of earth?
- Magma underground is less dense than the rocks that surround it.
Therefore, this property makes magma rise upward toward the surface.
11. How does a volcanic neck form?
- When a volcano stops erupting, magma hardens inside the vent. Erosion, by
water and wind, begins to wear away the volcano. The cone is much
shorter than the igneous rock in the vent, and tends to erode first, leaving
behind the igneous core as a volcanic neck.
12. If a lava is rich in IRON and MAGNESIUM then it is easy-flowing.
13. Compare and contrast dikes and sills.
- Dikes: magma that cuts across rock layers.
- Sills: Magma that cuts parallel to rock layers.
- Contrast: these two features form in opposite directions.
14. What is viscosity? How does it affect lava?
- Viscosity is the physical property of a fluid to resist flowing or not. It can
make lava flow easily or slowly.
15. What part of the volcano is the vent?
- The vent is the top/opening of the volcano where magma erupts from.
16. What part of the volcano is the magma chamber?
- The magma chamber is the bottom part of a volcano, underneath the
surface, where magma is stored before it erupts.
17. What are 4 dangers to people from volcanic eruptions?
-
Gas emissions released
Volcanic ash
Pyroclastic flow
Lahars
Lava flows
18. Name 3 warning signs of an impending volcanic eruption.
-
Smoke released from vent
Temperature changes
Water gets dirty
Gas emissions (example: helium)
Small earthquakes
Ground movements
19. Define caldera.
- It is large, sunken, usually circular depression that forms when the top of a
volcano collapses into the nearly empty magma chamber.
20. Define batholith.
- The largest intrusive igneous feature. They form when magma cools and
solidifies before reaching the surface. They take up a lot of space.
21. Define the following intrusive features.
a. Volcanic neck : Magma is left in the vent, dries up, and weathered from
wind and water.
b. Lava dome: Rounded volcanic feature that forms when a mass of
highly vicious lava slowly erupts from the vent.
22. Define the following volcanic hazards/what is the effect of each on humans, animals,
habitats, wildlife?
a. Lava flow: This hazard is not very dangerous for humans. It can
destroy wildlife and habitats. It erupts in quiet or explosive
eruptions.
b. Tephra: Solid fragments that include lava and volcanic pieces,
glass. Tephra can be exposed as volcanic ash.
c. Carbon dioxide: When exposed to wildlife in large amounts/
when in soaks soil, it can harm plants, trees, and wildlife in
general.
d. Sulfur dioxide: Sulfur dioxide and hydrogen sulfide gases when mixed
with water can form acidic rain. This rain can be harmful to animals
and vegetation.
e. Lahar: Rapidly flowing mixture of volcanic debris and water. When
human habitats are built in river valleys near volcanoes, the flow of
the debris can be directed toward the town, which can be harmful to
wildlife and habitats. Very little warning time.
f. Pyroclastic flow: Fast moving body of hot gases and solids. It can burn
and harm all forms of life in its path.
23. What are fissure eruptions AND where do they occur?
- FISSURE ERUPTIONS: When magma escapes from narrow and elongated cracks
in Earth’s crust, these eruptions occur. Fissure eruptions occur in the ocean
at divergent plate boundaries.
24. What is the effect of more gases in lava? What does it do to the eruption?
- More gases in lava can add to the pressure build up. This produces
explosive eruptions.