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LMS Ch 13.2 DR
Volcanic Eruptions Directed Reading
Question | Answer |
---|---|
Lava provides an opportunity for scientists to study?? | The nature of Earth’s crust and mantle. |
By analyzing the composition of volcanic rocks, geologists have concluded that there?? | Are two general types of magma. |
Magma or igneous rock that is rich in feldspar and silica and is generally light in color is called?? | Felsic. |
agma or igneous rock that is rich in magnesium and iron and is generally dark in color is called?? | Mafic. |
Mafic rock commonly makes up?? | Oceanic Crust. |
Felsic rock commonly makes up?? | Continental Crust. |
The force of a volcanic eruption is affected by?? | The viscosity of magma. |
Mafic magmas, with low viscosity and runny lava, cause?? | Quiet eruptions. |
Felsic magmas, with high viscosity and sticky lava, cause?? | Explosive eruptions. |
Explosive eruptions are most likely to be caused by magma with?? | Large amounts of trapped, dissolved gases. |
Oceanic volcanoes commonly form from?? | Mafic magma. |
Eruptions from oceanic volcanoes are usually?? | Quiet eruptions. |
When mafic lava cools rapidly it?? | Forms a crust. |
One of the most important warning signals of volcanic eruptions is?? | A change in earthquake activity around the volcano. |
Pyroclastic particles less than 2 mm in diameter that mostly fall on the land that immediately surrounds the volcano are called?? | Volcanic Ash. |
Pyroclastic particles less than 0.25 mm in diameter that are so small they might travel around Earth in the upper atmosphere are called?? | Volcanic Dust. |
Large pyroclastic particles less than 64 mm in diameter that generally fall near the vent are called , a name taken from a Latin word meaning “little stones.”?? | Lapilli. |
Large clots of lava thrown out of an erupting volcano while red-hot, that spin through the air, cool, and develop a round or spindle shape are called?? | Volcanic Bombs. |
The largest pyroclastic particles, which form from solid rock blasted from the volcano’s vent, are called?? | Volcanic Blocks. |
Pahoehoe?? | Forms a smooth, ropy texture as it cools. |
Aa Lava?? | Forms jagged, sharp chunks when it cools. |
Blocky Lava?? | Breaks into large chunks at the surface while hot lava continues to flow underneath. |
Volcanic Cone?? | Structure formed by lava and pyroclastic material ejected during volcanic eruptions. |
Crater?? | The funnel-shaped pit at the top of a volcanic vent. |
Shield Volcano?? | A volcanic cone that is broad at the base and has gently sloping sides. |
Cinder Cone?? | Volcano with very steep slopes that are rarely more than a few hundred meters high and have angles close to 40°. |
Composite Volcano?? | Volcano made of alternating layers of hardened lava flows and pyroclastic material. |