Unit 8 Volcanoes Flashcards

Questions and Answers

What is a hot spot?

An ocean ridge

A tectonic plate boundary

A place where volcanoes can be found (correct)

A region with frequent earthquakes

How is a hot spot related to a mantle plume?

Hot spots lie directly above mantle plumes.

Why do hotspot volcanoes form in lines?

Because the tectonic plates move above a hot spot.

What plate tectonic setting produces the most volcanoes?

At divergent plate boundaries and at convergent plate boundaries at subduction zones. Signup and view all the answers

Describe what happens during an explosive volcanic eruption.

An explosive eruption produces huge clouds of volcanic ash. Signup and view all the answers

Describe what happens during a non-explosive volcanic eruption.

Non-explosive eruptions produce thin, runny lava that flows easily. Signup and view all the answers

What are pyroclasts?

Hot fragments of rock. Signup and view all the answers

What is a magma chamber and what are its characteristics?

A magma chamber is an area where magma collects beneath Earth's surface. Signup and view all the answers

Why might water make an eruption more explosive?

Hot magma beneath the surface mixes with water, forming gases that increase pressure. Signup and view all the answers

Why is predicting volcanic eruptions so important?

Because volcanic eruptions can be devastating to nearby populations. Signup and view all the answers

What factors are considered in predicting volcanic eruptions?

Signs include an increase in earthquakes, surface bulging, and released gases. Signup and view all the answers

What is a composite volcano?

A composite volcano forms a tall cone shape with broad bases and steep sides. Signup and view all the answers

How does a composite volcano form?

It forms by alternating layers of magma and ash. Signup and view all the answers

What is a shield volcano?

Shield volcanoes are large, gently sloping volcanoes with a wide base. Signup and view all the answers

How does a shield volcano form?

It forms from thin lava that spreads out layer by layer. Signup and view all the answers

What is a cinder cone?

Cinder cones are small, cone-shaped volcanoes. Signup and view all the answers

How does a cinder cone form?

Cinder cones are formed from small fragments of rock called cinders. Signup and view all the answers

Study Notes

Hot Spots and Mantle Plumes

Hot spots are regions with volcanic activity, located often in the middle of tectonic plates.
Approximately 50 active hot spots exist on Earth, forming volcanoes above mantle plumes, which are columns of hot rock bringing magma from the mantle toward the crust.

Formation of Volcano Chains

As tectonic plates move over hot spots, they create a line of volcanoes, leading to the emergence of islands or elevated land.

Plate Tectonics and Volcanoes

Volcanoes predominantly occur at divergent boundaries (such as ocean ridges) and convergent boundaries in subduction zones.

Explosive Eruptions

Explosive volcanic eruptions generate vast clouds of ash and can release rock fragments high into the atmosphere.
Such eruptions can be 10,000 times more powerful than an atomic bomb, driven by gas pressure from hot magma mixing with water.

Non-Explosive Eruptions

Non-explosive eruptions are characterized by low gas content, resulting in thin, fluid lava that flows easily, resembling a river.

Pyroclasts

Pyroclasts are hot rock fragments expelled during volcanic eruptions.

Magma Chambers

Magma chambers are reservoirs beneath Earth's surface where magma accumulates, typically found at zones of high heat and pressure, like divergent and convergent boundaries or hot spots.

Water’s Role in Eruptions

Water can enhance the explosiveness of eruptions due to gas formation from hot magma interacting with water, increasing gas pressure until a large explosion occurs.

Importance of Prediction

Predicting volcanic eruptions is vital for minimizing potential devastation, especially for nearby populations.

Signs of Imminent Eruptions

Indicators of a possible eruption include increased seismic activity, surface deformation, and gas release that can be monitored by scientists.

Composite Volcanoes

Composite volcanoes feature tall, cone-shaped structures with broad bases and steep sides, often with large craters formed from past eruptions.

Formation of Composite Volcanoes

Alternating layers of magma and ash contribute to the formation of composite volcanoes, characterized by thick lava that creates steep sides due to limited lava flow.

Shield Volcanoes

Shield volcanoes are large with gently sloping sides and a broad base, appearing flatter on top compared to composite volcanoes, like Mauna Loa.

Formation of Shield Volcanoes

Thin lava spreads widely to create large flat structures in shield volcanoes, commonly formed at divergent plate boundaries and hot spots with non-explosive eruptions.

Cinder Cones

Cinder cones are small, cone-shaped volcanoes with steep sides, often less than 300 meters tall, and typically include a summit crater.

Formation of Cinder Cones

Formed from small rock fragments called cinders, cinder cones consist of piles of these fragments and rarely generate lava flows.

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Description

Explore the fundamentals of volcanoes through these flashcards from Unit 8. Learn about hot spots and their relation to mantle plumes, which are essential concepts in understanding volcanic activity. This quiz will enhance your knowledge of geological processes.