geo quiz 6
| Question | Answer |
|---|---|
| The big volcanoes of Hawaii | shield volcanoes |
| Which statement about the May, 1980, eruption of Mount St. Helens is FALSE? | During the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris. |
What was the cause of the May 1980 eruption of Mount St Helens?
With no immediate precursors, a magnitude 5.1 earthquake occurred at 8:32 a.m. on May 18, 1980 and was accompanied by a rapid series of events. At the same time as the earthquake, the volcano’s northern bulge and summit slid away as a huge landslide—the largest debris avalanche on Earth in recorded history.
What was unusual about the 1980 eruption of Mt St Helens quizlet?
The eruption was so large that the magma chamber under Crater Lake partially emptied, causing the volcano to become unstable and collapse.
What were the effects of the eruption of Mount St Helens in 1980?
57 people lost their lives and hundreds of homes, buildings and structures were destroyed. After the eruption, the summit of Mount St. Helens was gone, forests were obliterated and rivers followed new courses. More than 150 new lakes and ponds were formed, and existing lakes filled with sediment, flooding their banks.
What was formed following the 1980 eruption of Mt St Helens?
At the same time, snow, ice, and several entire glaciers on the volcano melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly 50 miles (80 km) to the southwest.
What caused the eruption of Mount St. Helens quizlet?
St. Helens erupted explosively. What triggered the eruption? The collapse of the north flank of the volcano produced a landslide‐debris avalanche.
What was unusual and damaging about the May 18 1980 eruption?
A high-speed blast leveled millions of trees and ripped soil from bedrock. The eruption fed a towering plume of ash for more than nine hours, and winds carried the ash hundreds of miles away. Lahars (volcanic mudflows) carried large boulders and logs, which destroyed forests, bridges, roads and buildings.
What are 5 interesting facts about Mt St Helens?
Here are five facts about the stratovolcano.
- Before erupting, the volcano was 9,677 feet.
- Over 230 square miles of forest was destroyed in minutes.
- The volcano has had numerous eruptions.
- The blast killed USGS scientist David Johnston.
- Native Americans abandoned hunting grounds at the volcano 3,600 years ago.
What killed the most people in the 1980 eruption of Mt St Helens?
asphyxiation
Fifty-seven people died when Mount St. Helens erupted in Washington on May 18, 1980 at 8:32 a.m. Autopsies showed that most of the people killed in the eruption likely died from asphyxiation after inhaling hot ash, according to the U.S. Geological Survey.
What was unique about the way Mt St Helens erupted?
A thermal shock wave zipped across the land before a tsunami of debris, cooking at 660 degrees Fahrenheit, traveled 17 miles from the summit in just three minutes. It destroyed 230 square miles of forested land: trees within six miles were obliterated; those farther out were knocked down and seared.
What went wrong Mount St. Helens?
A massive debris avalanche, triggered by a magnitude 5.1 earthquake, caused a lateral eruption that reduced the elevation of the mountain’s summit from 9,677 ft (2,950 m) to 8,363 ft (2,549 m), leaving a 1 mile (1.6 km) wide horseshoe-shaped crater. The debris avalanche was 0.6 cubic miles (2.5 km3) in volume.
What were three effects that the eruption of St Helens had on the surrounding environment?
Helens’ vicitims died by asphyxiation from inhaling hot volcanic ash, and some by thermal and other injuries. The lateral blast, debris avalanche, mudflows, and flooding caused extensive damage to land and civil works. All buildings and related manmade structures in the vicinity of Spirit Lake were buried.
What happened during St Helens eruption?
Mount St. Helens’ volcanic cone was completely blasted away and replaced by a horseshoe-shaped crater–the mountain lost 1,700 feet from the eruption. The volcano produced five smaller explosive eruptions during the summer and fall of 1980 and remains active today.
What types of volcanic hazards occurred during the 1980 eruption of Mount St. Helens?
News archive. Ten years ago, on May 18, 1980, Mount St. Helens volcano erupted cataclysmically, producing a huge debris avalanche, an explosive, laterally direction “blast”, lahars, and a Plinian eruption column. This powerful eruption had a profound impact on the Pacific Northwest – and on volcano studies as well.
How much of Mount St. Helens was blown off during the 1980 eruption?
1980: Washington state’s Mount St. Helens volcano explodes in a cataclysm that pulverizes its top 1,300 feet, deforests nearby valleys, sends ash 12 miles into the air and kills 57 people.
What tectonic plates caused Mount St. Helens eruption?
In Mount St. Helens’ case, an oceanic plate called Juan de Fuca slips under the North American plate, creating the Cascadia subduction zone. A continental arc brews adjacent to the subduction zone, where high pressures and hot temperatures force molten rock to the surface. The result is a chain of volcanoes.
What are main causes of the eruption?
Although there are several factors triggering a volcanic eruption, three predominate: the buoyancy of the magma, the pressure from the exsolved gases in the magma and the injection of a new batch of magma into an already filled magma chamber. What follows is a brief description of these processes.
What type of volcano is Mount St. Helens and what caused the explosion quizlet?
What type of volcano is Mount St. Helens and what caused the explosion? It is a strato-volcano that exploded when trapped gasses were quickly released. The most violent volcanic eruptions occur when gasses cannot easily escape from the magma.
What type of volcano is Mount St. Helens and what caused the explosion?
Mount St. Helens, a stratovolcano or composite volcano located in Washington State, USA (46.2º latitude north, 122.2º longitude west,) erupted violently on the Sunday morning of May 18th 1980 at precisely 8:32.
How does the May 18 1980 eruption of Mount St. Helens compare to a typical eruption?
Considered barely “very large,” the eruption of Mount St. Helens in May 1980 was smaller than most other “very large” eruptions within the past 10,000 years and much smaller than the enormous caldera-forming eruptions–which would rate VEl’s of 8–that took place earlier than 10,000 years ago.
How does the May 18 1980 eruption of Mount St. Helens compare to a typical eruption of Hawaii’s Kilauea volcano?
Mount St. Helens’ magma is inherently more explosive than the Kīlauea magma: it has more water in it than Kīlauea magma, and is delivered to the surface at a higher pressure because of higher magma viscosity. So Mount St. Helens tends to have explosive eruptions and Kīlaueaa eruptions are generally non-explosive.