- What are four different landforms created by lava?
- What is the major difference between hot springs and geysers?
- The geyser called Old Faithful has been erupting for perhaps hundreds of years. One
day, it could stop. Why might geysers completely stop erupting? - After earthquakes, hot springs sometimes stop bubbling, and new hot springs form.
Why might this be?
Vocabulary
intrusive Describing a volcanic rock that cooled underground. Intrusive rocks contain
large mineral crystals that are visible to the naked eye.
extrusive Describing a volcanic rock that cooled at the earth’s surface. Extrusive rocks
have small crystals, and may contain air bubbles.
lava dome A dome-shaped plug of viscous lava that cools near the vent of a volcano.
intrusion A rock mass formed by magma solidifying underground.
hot spring A stream of hot water that flows out of the ground continuously.
geyser A fountain of hot water and steam that shoots into the air at either regular or
random intervals. The water in a geyser encounters some sort of constriction under-
ground, which forces pressure to build up in the water, eventually causing the geyser
to erupt.
Points to Consider
- What might the Earth look like if there were no tectonic plates? Can you think of any
planets or satellites (moons) that may not have tectonic plates? How is their surface
different from that of the Earth? - What kind of land formations have you seen that may have been created by volcanic
activity? Were the formations made of extrusive or intrusive rock? - Water is not the only material that can be ejected from geysers and hot springs.
Consider the composition of the Earth’s crust. What other materials might be ejected
from geysers and hot springs?