Volcanic eruption how does it happen

Explosive volcanic eruptions can be dangerous and deadly. They can blast out clouds of hot tephra from the side or top of a volcano. These fiery clouds race down mountainsides destroying almost everything in their path.

Ash erupted into the sky falls back to Earth like powdery snow. If thick enough, blankets of ash can suffocate plants, animals, and humans. When hot volcanic materials mix with water from streams or melted snow and ice, mudflows form. Mudflows have buried entire communities located near erupting volcanoes.

Despite their seeming permanence, volcanoes are prone to catastrophic collapse that can affect vast areas in a matter of minutes. Large collapses begin as gigantic landslides that quickly transform to debris avalanches—chaotically tumbling masses of rock debris that can sweep downslope at extremely high velocities, inundating areas far beyond the Ash, mudflows, and lava flows can devastate communities near volcanoes and cause havoc in areas far downwind, downstream, and downslope.

Even when a volcano is quiet, steep volcanic slopes can collapse to become landslides, and large rocks can be hurled by powerful When erupting, all volcanoes pose a degree of risk to people and infrastructure, however, the risks are not equivalent from one volcano to another because of differences in eruptive style and geographic location.

Assessing the relative threats posed by U. At least volcanoes in 12 States and 2 territories have erupted in the past 12, years and have the potential to erupt again. Consequences of eruptions from U. Many aspects of our daily life are vulnerable to volcano hazards, On May 22, , a large explosive eruption at the summit of Lassen Peak, California, the southernmost active volcano in the Cascade Range, devastated nearby areas and rained volcanic ash as far away as miles to the east.

This explosion was the most powerful in a series of eruptions during —17 that were the last to occur in the Viewing an erupting volcano is a memorable experience, one that has inspired fear, superstition, worship, curiosity, and fascination since before the dawn of civilization.

In modern times, volcanic phenomena have attracted intense scientific interest, because they provide the key to understanding processes that have created and shaped more than Volcanoes have been erupting in the Cascade Range for over , years. During the past 4, years eruptions have occurred at an average rate of about 2 per century. This chart shows 13 volcanoes on a map of Washington, Oregon, and northern California and time lines for each showing the ages of their eruptions. Most volcano hazards are associated with eruptions.

However, some hazards, such as lahars and debris avalanches, can occur even when a volcano is not erupting. Our Earth is a dynamic planet, as clearly illustrated on the main map by its topography, over volcanoes, 44, earthquakes, and impact craters. These features largely reflect the movements of Earth's major tectonic plates and many smaller plates or fragments of plates including microplates.

Volcanic eruptions and earthquakes are awe Volcanoes is an interdisciplinary set of materials for grades Through the story of the eruption of Mount St. Helens, students will answer fundamental questions about volcanoes: "What is a volcano?

Volcanoes give rise to numerous geologic and hydrologic hazards. Geological Survey USGS scientists are assessing hazards at many of the almost 70 active and potentially active volcanoes in the United States.

They are closely monitoring activity at the most dangerous of these volcanoes and are prepared to issue warnings of impending In the early s, the emergence of the theory of plate tectonics started a revolution in the earth sciences.

Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics Helens was waking up. Within a week, several eruptions blasted clouds of ash into the atmosphere, and soon after, a new lava dome emerged in the crater. The HVO. Tephra blasted from the summit vent on Saturday night included lithic solid rock fragments from the vent wall as well as spatter molten lava fragments ejected from the lava lake.

The light-colored lithic in the center of this photo is about 20 cm 8 in long—the GPS unit is shown for scale. Tephra, the general term for volcanic rock fragments exploded or carried into. The United States has active volcanoes. More than half of them could erupt explosively, sending ash up to 20, or 30, feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.

It can spread over large areas as the lava continues to flow underneath. Pillow Lava Pillow lava is lava that comes out from volcanic vents underwater Figure 8. When it comes out underwater, it cools down very quickly and forms roughly spherical rocks that resemble pillows, from which more lava leaks and creates more pillows. Pillow lava is particularly common along underwater spreading centers. Predicting Volcanic Eruptions Volcanic eruptions can be devastating, particularly to the people who are closer to volcanoes.

As meteorologists attempt to predict, or forecast, hurricanes and tornadoes, so too do vulcanologist attempt to forecast volcanic eruptions.

Although predicting volcanic eruptions is far from perfect, many pieces of evidence can indicate that a volcano is about to erupt. Some of those factors are hard to measure, contributing to the difficulty in predicting eruptions. That is, we consider how long since it has erupted and the time span between its previous eruptions.

Volcanoes are categorized into three subdivisions—active, dormant, and extinct. An active volcano is one that is currently erupting or shows signs of erupting in the near future. A dormant volcano no longer shows signs of activity, but has erupted in recent history Figure 8. Finally, an extinct volcano is one that has not erupted in recent history and will probably not erupt again in the future.

Both active and dormant volcanoes are heavily monitored because even dormant volcanoes could suddenly show signs of activity. Although it shows no current signs of eruption, it could one day become active.

Earthquakes As magma beneath a volcano pushes upward, it shakes the ground and causes earthquakes. Although earthquakes probably occur every day near a volcano, the quantity and size of the earthquakes increases before an eruption. In fact, a volcano that is about to erupt may produce a continuous string of earthquakes, as magma moving underground creates stress on the neighboring rocks.

In order to measure these earthquakes, scientists use seismographs that record the length and strength of each earthquake. Sometimes, ground swelling reveals huge changes in the shape of a volcano. Most cases of ground deformation are subtle, though, and can only be detected by tiltmeters, which are instruments that measure the angle of the slope of a volcano.

Additionally, ground swelling may cause increased rock falls and landslides. Oftentimes, gases are able to escape a volcano before magma reaches the surface in an eruption. So, scientists can measure gas output, or gas emissions, in vents on or around the volcano. Gases, like sulfur dioxide SO 2 , carbon dioxide CO 2 , hydrochloric acid HCl and even water vapor can be measured at the site or, in some cases, at a distance with satellites. The amounts of gases and their ratios are calculated to help predict eruptions.

As mentioned, some gases can be monitored using satellite technology Figure 8. Satellites are able to measure other factors, too, like temperature readings of particularly warm spots at a volcano site or areas where the volcano surface is changing. As our technology continues to improve, scientists are better able to detect changes accurately and safely. Although monitoring methods are getting better and better, it is still difficult to predict a volcanic eruption with certainty.

The cost and disruption to society of a large-scale evacuation would leave many people displeased and the scientists embarrassed. However, the possibility of saving lives and property most certainly makes the pursuit of eruption prediction a worthy cause. Skip to main content. Search for:. Volcanic Eruptions In , Mount St. Licenses and Attributions.

Be aware of secondary risks such as landslides and flash floods. Support vulnerable people to evacuate or shelter in place safely. Prepare and practice evacuating or sheltering in place.

Watch: how to prepare for a volcanic eruption. Featured document. Volcanoes: Key Messages. Related links. What is a disaster? Prepare your family and home. Create a List. List Name Save. Rename this List. Rename this list. List Name Delete from selected List. Save to. Save to:. Save Create a List. Create a list. Save Back. Volcanic Eruptions. Grades 3—5 , 6—8 , 9— View not found. Download the PDF from here.

Related Subjects. Appears in This Collection. Grade s K About Us.