12 Questions
What drives magma towards Earth's surface?
Buoyancy and pressure from gas within it
How are cinder cone volcanoes formed?
By accumulation of solid lava pieces ejected during eruption
What is the primary factor causing volcanic eruptions?
Magma pressure and weak areas in the Earth's crust
Where are most of the potentially active volcanoes located in the United States?
Alaska
Which type of volcanic eruption results in the ejection of dense clouds of rock shards and gas?
Strombolian eruptions
What is the distinctive characteristic of Kīlauea volcano on the Island of Hawai‘i?
Nonstop erupting since 1983
What is the main way volcanic terrain is formed?
Slow accumulation of erupted lava
What connects the volcanic vent to the magma storage areas?
A series of cracks
What happens when a volcano is no longer stable?
Pieces of the volcano collapse
What is magma made of?
Molten rock, crystals, and dissolved gas
What happens when liquid magma cools?
It forms an igneous rock
Why is magma lighter than the surrounding solid rock?
Because it originates from deep beneath the ground
Study Notes
Volcano Formation and Eruption
- Magma is driven towards Earth's surface by buoyancy and pressure from gas within it
- Magma forces its way upward and may break through weak areas in the Earth's crust, causing an eruption
- Eruptions can occur in various ways, including pouring out as fluid lava flows or shooting violently into the air as dense clouds of rock shards and gas
Types of Volcanoes
- Cinder cones are the simplest type of volcano, formed from small pieces of solid lava that erupt from a vent
- Cinder cones can grow up to 1,000 feet tall and accumulate in an oval shape if the wind is blowing during the eruption
Volcano Facts
- There are over 160 active and potentially active volcanoes in the United States, mostly located in Alaska and Hawaii
- Kīlauea volcano on the Island of Hawai‘i is one of the most active volcanoes on Earth, erupting almost nonstop since 1983
- There are about 1,350 potentially active volcanoes worldwide, not counting those under the oceans
- About 500 of these have erupted in the past 100 years, many of which are located around the Pacific Ocean in the "Ring of Fire"
Magma and Lava
- Magma is molten rock below the surface of the Earth that rises in volcanic vents
- Magma is made of molten rock, crystals, and dissolved gas
- Once erupted from a volcano, magma is called lava
- Lava cools and solidifies to form an igneous or magmatic rock
Learn about how volcanic terrains are formed through the accumulation of erupted lava, and how vents connect to storage areas of magma beneath the Earth's surface. Discover the structure and processes of volcano formation.
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