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Transcript of volcanoes
How frequently does a volcano occur?
Well that depends on the volcano. Some volcanoes erupt very often (and some like Kilauea almost never stop). On the other hand, some volcanoes are inactive for very long periods of time between eruptions. For example Mt. St. Helens erupted in the late 1800's and then again in 1980.
what is a volcano
It's a mountain or hill typically conical, having a crater or vent through which lava, rock fragments, hot vapor, and gas are being or have been erupted from the earth's crust.
What does a volcano cause
It cause massive destitution! It opens downward to a pool of molten rock below the surface of the earth. When pressure builds up, eruptions occur. In an eruption, gases and rock shoot up through the opening and spill over or fill the air with lava fragments.
How does volcanoes affect the environment
Plants are destroyed over a wide area, during an eruption. The good thing is that volcanic soil is very rich, so once everything cools off, plants can make a big comeback!
Mount St. Helens provides an example. The Washington Department of Game estimated that 11,000 hares, 6,000 deer, 5,200 elk, 1,400 coyotes, 300 bobcats, 200 black bears, and 15 mountain lions died from the pyroclastic flows of the 1980 eruption
pictures of an active volcanoes
Livestock and other mammals have been killed by lava flows, pyroclastic flows, tephra falls, atmospheric effects, gases, and tsunami. They can also die from famine, forest fires, and earthquakes caused by or related to eruptions.lated to eruptions.
where do volcanoes usually occur
Most volcanoes occur near the edges of plates. When plates push together, one plate slides beneath the other. This is a subduction zone. When the plunging plate gets deep enough inside the mantle, some of the rock on the overlying plate melts and forms magma that can move upward and erupt at the Earth's surface.
how can volcanoes be predicted
The prediction of volcanic eruptions is difficult because, to be of practical use, they must be made before eruptions! Its a lot easier to see patterns in monitoring data after an eruption has occurred. But great progress has been made because of the lessons learned over many years
how is a volcano measured and classified
Volcanic eruptions vary in size and explosiveness. Volcanologists take a number of factors into account when they determine the "bigness" of a volcanic eruption. As you can see from the chart below, small volcanoes occur more frequently and truly colossal volcanoes don't happen very often (whew). For a large eruption, it takes much time for gas pressures to build up.
how can a person can be prepare for a volcanic eruption
Mudflows- Mudflows are powerful “rivers” of mud that can move 20 to 40 mph. Hot ash or lava from a volcanic eruption can rapidly melt snow and ice at the summit of a volcano. The melt water quickly mixes with falling ash, with soil cover on lower slopes, and with debris in its path. This turbulent mixture is dangerous in stream channels and can travel more than 50 miles away from a volcano. Intense rainfall can also erode fresh volcanic deposits to form large mudflows. If you see the water level of a stream begin to rise, quickly move to high ground. If a mudflow is approaching or passes a bridge, stay away from the bridge. Avoid river valleys and low lying areas. Trying to watch an erupting volcano up close is a deadly idea.
Have a plan to escape from the volcanic eruption. Don't wait out the volcanic eruption because that is dangerous to you and your family.
MT. ST. Helens 1980s
The 1980 eruption of Mt. St. Helens is the most studied volcanic eruption of the twentieth century. Although most people were unaware of the potential for such a violent display of volcanism in the contiguous U.S., volcanologists were keenly aware of the potential danger. Months before it erupted, the U.S. Geological Survey (USGS) established a base of operations at Vancouver, Washington to monitor the volcano. On May 18, survey volcanologist David Johnston was camping on Coldwater Ridge, only a few miles north of Mt. St. Helens. The eruption occurred that morning. At 8:32 a.m., Johnston radioed the USGS base and exclaimed "Vancouver, Vancouver, this is it!" The ensuing volcanic blast devastated the northern flank of the volcano, killing Johnston and 56 other victims. At the same time, geologists Keith and Dorothy Stoffel were flying in a light plane only 400 meters above the summit of Mt. St. Helens. From their vantage point, they witnessed one of the largest landslides ever recorded in historic times. Seconds later, a massive explosion shot out the north side of the volcano, toward Coldwater Ridge and Spirit Lake. The explosion generated a billowing cloud with numerous lightning bolts thousands of meters high. The cloud began to expand rapidly toward their aircraft and appeared to be gaining on them, but by turning south they managed to outrun it and survive.