Geology Chapter 4, 5 & 6 Review

Questions and Answers

Where does the lava come from for volcanic island arcs and continental volcanic arcs?

Volcanic island arcs are constructed on oceanic lithosphere, while continental volcanic arcs see rising mantle-derived magma assimilate continental material.

How is magma like a bottle of soda, and what happens to both substances when the pressure changes?

Both magma and soda contain dissolved gases that are kept in solution under high pressure. When pressure changes, gas bubbles can form.

What is the importance of monitoring volcanic activity?

To prevent potential disruptions to business and travel and to protect populations from eruptions.

How can climate affect the weather?

Cold and dry conditions result in mechanical weathering, while warm and wet conditions lead to chemical weathering. Signup and view all the answers

Provide an example of a positive aspect of weathering.

Weathering produces soil, which is essential for growing food. Signup and view all the answers

How can sulfur dioxide gas erupted from a volcano affect global climate?

It forms reflective aerosols of sulfuric acid that can cool temperatures by reflecting solar radiation. Signup and view all the answers

What is the temperature at a depth of 2 miles, assuming a surface temperature of 20 degrees Celsius?

64 degrees Celsius. Signup and view all the answers

How would the geothermal gradient change if a borehole were drilled near Yellowstone National Park?

The geothermal gradient would be significantly higher. Signup and view all the answers

How do scientists use earthquakes to predict potential volcanic eruptions?

Increasingly shallow earthquakes centered under a volcano indicate magma movement into the magma chamber. Signup and view all the answers

Why isn't quartz considered a ferromagnesian mineral despite the original melt containing iron?

Early-forming minerals like olivine remove iron from the melt during crystallization. Signup and view all the answers

Which type of volcano is considered the most dangerous to live near, and why?

Composite cone volcanoes due to their violent eruptions and hazards like pyroclastic flows. Signup and view all the answers

Study Notes

Volcanic Island Arcs vs. Continental Volcanic Arcs

Volcanic island arcs form on oceanic lithosphere and primarily produce basaltic lava due to flux melting and interaction with oceanic lithosphere.
Continental volcanic arcs derive from rising mantle-derived magma that assimilates silica-rich continental material, leading to the production of andesitic or rhyolitic magmas.

Magma and Soda Analogy

Both magma and soda contain dissolved gases, which remain in fluid form under high pressure.
When pressure decreases, gas bubbles can form, leading to eruptive activity in magmas, similar to carbonation loss in opened soda bottles.

Importance of Monitoring Volcanic Activity

Volcanoes near population centers can significantly disrupt business, travel, and pose risks to human life during eruptions.

Climate's Effect on Weathering

Cold and dry climates promote mechanical weathering processes.
Warm and wet climates favor chemical weathering, altering geological materials.

Positive Aspects of Weathering

Weathering is essential for soil production, necessary for agriculture.
It provides materials for artistic endeavors and exposes economically valuable deposits through erosion.

Sulfur Dioxide and Global Climate

Sulfur dioxide gas can bond with atmospheric water, forming reflective aerosols that cool the Earth's surface by reflecting solar radiation.

Calculating Temperature at Depth

At a depth of 2 miles (3.2 km) below the surface, the temperature is calculated to be approximately 64 degrees Celsius, based on a gradient of 20 degrees C/km.

Geothermal Gradient near Yellowstone

The geothermal gradient in areas like Yellowstone is higher due to geologically recent volcanic activity and proximity of magma to the surface.

Earthquakes and Volcanic Eruption Prediction

Shallow earthquakes beneath a volcano signal magma movement toward the surface, with increasing seismic unrest often preceding violent eruptions.

Ferromagnesian Minerals and Cooling Magma

Early crystallizing minerals, such as olivine, sequester iron in solid form, preventing quartz and later minerals from incorporating iron into their structures.

Dangers of Composite Cone Volcanoes

Composite cone volcanoes are highly dangerous due to violent eruptions that generate pyroclastic flows, ash falls, and lahars. These hazards can lead to substantial damage and casualties, affecting areas far from the volcano itself.

Description

Prepare for your Geology tests with this comprehensive review on Chapters 4, 5, and 6. Explore key concepts such as volcanic island arcs and their associated lava sources. This flashcard set will enhance your understanding of convergent plate boundaries and their characteristics.