Features formed by volcanic activity
Lava plateau
- when fluid lava flows out of cracks creating a flat horizontal feature with multiple layers
Volcano
- comes from Vulcan-the roman God of Fire
-formed when a mound of lava develops with a slope of a few degrees
or more.
3 types of volcanoes
1. Shield Volcano-
-forms from successive eruptions of fluid
basaltic lava.
-has broad, gently sloping sides and a nearly circular base
-made up entirely of layers of lava rock
-example would be Hawaiian Islands
2. Cinder-cone volcano-
-forms as expanding gases throw volcanic material high into the air and it then piles up around central vent or crack.
-has steep sides with concave slopes
-made up of layers of loose lava rock and ash
-smaller than shield volcanoes but more explosive due to thicker lava
-example would be Paracutin, near Mexico City
3. Composite volcano-
-forms from alternating layers of lava and volcanic rock fragments piling up
-has steep sides
-very thick lava makes them most explosive type of volcano
-example would be Mt. St. Helens
Dangers of Volcanoes
a. Produce explosive force
b. Produce poisonous gases
c. Pyroclastic flow-extremely hot cloud of gas, ash, and other materials that travel down slopes of volcano at speeds up 200km/h.
d. Volcanic ash-can bury houses, start fires and may mix with melting snow, ice or glaciers to produce mudslides.
e. Flooding from melting snow, ice or glaciers
f. Lava flows
g. Falling rocks called “bombs”
h. Tsunamis if they erupt under water
i. Earthquakes or tremors
Signs of an Eruption
Special tools are used to monitor the possibility of an eruption.
1. Satellites- monitor changes in heat energy given off by rising magma beneath the earth’s surface.
2. Tilt meters- measure the change in a volcano’s slope as magma increases inside it.
3. Seismographs- monitor earthquakes and tremors associated with movement of magma within the volcano.
4. Benchmarks- changes in a volcano’s elevation are noted by looking to see how much the benchmark has moved up.
Using these types of monitors especially around active volcanoes can help scientists to predict an eruption sometimes within an hour of it actually occurring.