St. Helens has been studied experimentally and found to have a viscosity that declines from about 1015 at 800°C to 103 poise at 1500°C.
What type of lava does Mt St Helens have?
The range of rock types erupted by the volcano changed about 2,500 yr ago, and since then, Mount St. Helens repeatedly has produced lava flows of andesite, and on at least two occasions, basalt.
What is the viscosity of lava?
The viscosity of most lava is about that of ketchup, roughly 10,000 to 100,000 times that of water.
Which lava is more viscous?
Thus, basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water. Rhyolitic magmas tend to have even higher viscosity, ranging between 1 million and 100 million times more viscous than water.
Is there lava flow from Mt St Helens?
Lava flows from Mount St. Helens typically affect areas within 6 mi (10 km) of the vent. However, two basalt flows erupted about 1,700 years ago extended about 10 mi (16 km) from the summit; one of them contains the Ape Cave lava tube.
Is Mt St Helens quiet or explosive?
Helens has displayed both relatively quiet outpourings of lava and violent explosive eruptions of volcanic ash and rock fragments, known as tephra. Volcanologists have separated the eruption history of this volcano into four main stages, each followed by a dormant, nonexplosive period.
Is Mount St. Helens explosive or quiet?
Helens and other volcanoes in the Cascades arc due to subduction of the Juan de Fuca plate off the western coast of North America. Over its rich and complex 275,000-year history, Mount St. Helens has produced both violent explosive eruptions of volcanic tephra and relatively quiet outpourings of lava.
Which lava is the least viscous?
Differences in a magma’s viscosity will determine the shape a volcano takes. High-silica (basalt) magma has a much lower viscosity. It flows much easier and over longer distances.
What happens if you touch lava?
Lava won’t kill you if it briefly touches you. You would get a nasty burn, but unless you fell in and couldn’t get out, you wouldn’t die. With prolonged contact, the amount of lava “coverage” and the length of time it was in contact with your skin would be important factors in how severe your injuries would be!
Is viscous lava hotter?
Temperature, composition, and volatile (gas) content largely determine the viscosity of lava. Temperature: The hotter the lava, the lower the viscosity (the thinner it is). The cooler the lava, the higher the viscosity (the thicker it is).
How hot is blue lava?
10,830 °F
Actual lava is red-orange in color, given its temperature. Truly-blue lava would require temperatures of at least 6,000 °C (10,830 °F), which is much higher than any lava can naturally achieve on the surface of the Earth.
What type of volcano is highly viscous?
Stratovolcano Stratovolcanoes
Stratovolcano. Stratovolcanoes have relatively steep sides and are more cone-shaped than shield volcanoes. They are formed from viscous, sticky lava that does not flow easily.
Is lava a fire or earth?
Both fire and eruptions were viewed as mysterious natural sources of heat that must somehow be related. But we have made progress in understanding nature. We now know that lava (and its underground equivalent, magma) is formed, not by burning anything, but by slow heating under great pressure within the earth.
How far did the lava travel in Mt St Helens?
| Volcano | |
|---|---|
| Area covered | 6 square miles; reached as far as 5 miles north of crater |
| Volume & depth* | 0.029 cubic miles (155 million cubic yards); multiple flows 3 to 30 feet thick; cumulative depth of deposits reached 120 feet in places |
| Velocity | Estimated at 50 to 80 miles per hour |
| Temperature | At least 1,300¡ F (700¡ C) |
Will Mt St Helens ever erupt again?
We know that Mount St. Helens is the volcano in the Cascades most likely to erupt again in our lifetimes. It is likely that the types, frequencies, and magnitudes of past activity will be repeated in the future.
How loud was Mt St Helens?
163 decibels
On 18th May 1980, Mount St Helens erupted in Skamania County, Washington. The force was enough to blow down trees 16 miles away and it was seen on the Space Shuttle from outer space. The sound measured 163 decibels and the force blew windows out up to 200 miles away in Seattle!
What is the loudest volcano?
The loudest sound in recorded history came from the volcanic eruption on the Indonesian island Krakatoa at 10.02 a.m. on August 27, 1883.
Which volcano is loudest sound?
of Krakatoa
On the morning of 27 August 1883, on the Indonesian island of Krakatoa, a volcanic eruption produced what scientists believe to be the loudest sound produced on the surface of the planet, estimated at 310 decibels (dB).
Does Mt St Helens have high viscosity?
In contrast, lava of volcanoes located along plate margins, such as Mount St. Helens, generally is more viscous (“stickier” and “stiffer”) and tends to fragment, often very explosively, during eruption. Highly fluid lava favors the nonviolent release of the expanding volcanic gases that drive eruptions.
What kind of viscosity does Mt St Helens have?
St. Helens has been studied experimentally and found to have a viscosity that declines from about 10 15 at 800°C to 10 3 poise at 1500°C. Its yield strength declines from about 2 × 10 6 dynes cm –2 at 800°C to less than the precision of our measurements (10 4 dynes cm –2) above 1050°C.
What is the least explosive eruption?
The six eruption types are in order from least explosive to the most explosive; Icelandic, Hawaiian, Strombolian, Vulcanian, Pelean, and Plinian.