Chapter 5- Volcanic Eruptions Flashcards
What is a volcano?
An erupting vent through which molten rock surfaces, or, a mountain built from magmatic eruptions.
When did mount Vesuvius erupt and how many people were killed from the pyroclastic flow?
It erupted in 79 A.D. And killed 20,000 people in Pompeii
What is the difference between effusive and explosive volcanoes?
Effusive volcanoes erupt into lava flows while explosive volcanoes erupt in pyroclasts(volcanic fragments)
What is viscosity?
It is a measure of a materials resistance to flow. E.g. Honey has high viscosity.
What affects viscosity?
Temperature and composition(higher silica content equals higher viscosity) and gasses
What type of lava does a basaltic lava flow have?
It has magic lava which is hot with low silica content and viscosity.
How fast and far can a basaltic lava flow go?
It an travel up to100 km an hour and at distances up to 100 km
What is pahoehoe(pahoyhoy)?
It is a basaltic lava flow with glassy ropy texture
What is a’a’(ah-ah)?
It is a basaltic lava that solidifies with an angular jagged surface.
What is columnar jointing?
When lava cools into vertical hexagonal columns
How are pillow basalts formed?
It is a mound of lava from a mid ocean ridge that cools instantly into a round ball or “pillow”
What is an andesitic lava?
It is high in silicates and thus very viscous. Slow moving flow that stays close to the vent.
What is a rhyolitic lava?
It has the highest silicate content and thus is the most viscous lava. Usually plugs the vent as a lava dome.
What is a volcaniclastic deposit?
It is fragments of igneous materials accumulated in a cooled flow.
What are the three types of pyroclastic material?
Pyroclasts, tuff, and specific pyroclast types
What are the specific pyroclast types?
Pumice-rhyolite with an abundance of vesicles
Scoria- pumice of basaltic composition
Cinder-lapilli-size basaltic pumice
What is tuff?
Rock resulting from pyroclastic deposit
What are the three types of pyroclasts?
Volcanic ash, lapilli, and bombs
What are the three types of pyroclastic transport?
Pyroclastic fallout(ejection into air rains like snow) Pyroclastic flow(horizontal ejection of ash that ride on hot gas. Lahar(volcanic mudflow)
What is pele’s hair?
Strands of glass created by flying lava droplets
Why do intermediate and felsic magmas erupt more explosively?
Because they are more viscous than basaltic magma and they produce more ash
True or false? Pyroclastic flows can range in temperature from 100 to 325 degrees Celsius.
False, they range from 200 to 450 degrees Celsius
True or false? Pyroclastic flows can move up to 300 kilometers per hour.
True
What are three examples of volcanoes with pyroclastic flow?
Mt. Vesuvius, mt. Pelee, and mt. Augustine
How fast can lahars move?
Up to 50 km per hour
True or false? 20% of magma is gas.
False, gas content in magma can go as high as 9%
What are the most abundant gasses in magma in order of abundance?
Water
Carbon dioxide
Sulfur dioxide
True or false? Gas is expelled as magma rises.
True
How does gas escape affect eruption?
Low viscosity(gasses escape early, mellow eruption) High viscosity(gasses are trapped, violent eruption)
What are gas bubbles in rock called?
Vesicles
What is a crater?
A bowl shaped depression atop a volcano
What is a caldera and how long is their typical width?
It’s a gigantic volcanic depression formed from massive eruptions that collapse the volcano. They range from 1-10 km in width
What are some famous calderas?
Crater lake Oregon
Yellowstone national park
What is a shield volcano?
It is a large volcano that is short but very wide due to low viscosity basaltic lava flows
What is a cinder cone volcano?
It is a cone shaped pile of tephra that is comprised of lapilli piled up at the vent. It is the smallest type of volcano
What are stratovolcanoes?
Large cone shaped volcanoes composed of alternating layers of tephra and lava, often symmetrical.
What are some examples of a stratovolcano?
Mt. Fuji, mt. Rainier, mt. Vesuvius
When did mt. St. Helen’s erupt?
May 18 1980 8:32 a.m.
How far away did ash travel from mt. St. Helen’s?
North Dakota
At what type of plate boundary do most volcanoes emerge?
Convergent boundaries
How much greater was the Yellowstone eruption compared to mt. St. Helen’s?
1000 time greater
What is an active volcano?
It is a volcano that is erupting has recently erupted or is likely to erupt.
What is a dormant volcano?
It is a volcano that has not erupted for hundreds to thousands of years.
What is an extinct volcano?
It is a volcano that is no longer capable of erupting.
What are the four warning signs that an eruption is about to occur?
Earthquake activity
Heat flow(magma causes volcanoes to heat up)
Changes in shape(volcanoes will inflate)
Changes in gas mix and volume
What is lunar Maria?
Dark spots on the moon that are regions of flood basalts
