week 8

Which is the most accurate statement about viscosity and magma? Select one: a. The viscosity of magma is dependent on the amount of gas dissolved in the magma b. Magmas from composite volcanoes have relatively high viscosity c. High viscosity magmas flow at higher speeds than low viscosity magmas d. Mafic magmas are hotter and have higher viscosity than felsic magmas Feedback

B

Basalt is the principal component of which of the following features? Select one or more: 1. shield volcanoes 2. composite volcanoes 3. oceanic crust 4. continental crust

1,3

Which of the following types of volcanoes form triangular-shaped mountains in profile view? (select all that apply)

A. composite volcanoes B. shield volcanoes

A lahar forms when magma from a volcano interacts with material from what other part of the earth system

Hydrosphere

Which of the following statements most accurately summarizes volcanic activity in the states of Washington and Oregon.

Seattle is located to the west of the active volcanoes in the Cascade Range. These composite volcanoes have erupted on average 1-2 times per century during the past 4000 years and are formed above a subduction zone on the North American plate where it collides with the Juan de Fuca plate.

Tephra and lahar deposits can both include fine-grained particles as well as boulder-sized materials. Select one: True False

T

Which of the following are indicators of a caldera eruption? (select all that apply) Learning Objective: I can sketch the formation of a caldera and explain why these types of eruptions are so destructive. Choices: A. pillow lavas B. flood basalts C. mountains associated with a subduction zone D. a crater that is tens of kilometers across E. a thick layer of tuff over a large area

d,e

cinder cone

explosive liquid lava; small; potentially high gas content

A caldera is has a smaller eruptive potential than a composite volcano because it is a much shorter feature (i.e., not a mountain). t/f

f

Which volcanic hazard is most likely to cause destruction in some towns located 30-60 kilometers away from a Cascade Range volcano? Select one: a. lava flows b. lahars c. pyroclastic flows

lahars

Which of the following ground-based volcanic hazards associated with the eruption of Mt. Saint Helens (i.e., not tephra) covered the largest amount of the surrounding area?

lateral blast deposits

shield volcano

low viscosity liquid lava emitted from a central vent; large

Which pair of terms would make the best match to fill the blanks in the following sentence? Gases escape more easily from a viscosity magma; that is why eruptions are more violent from volcanoes that are supplied by viscosity magma.

low, high

Composite/Stratovolcano

more viscous lavas, much explosive (pyroclastic) debris; large, emitted from a central vent

lava flows form often in association with

shield volcanoes

Which eruption product travels farthest from the volcano?

tephra

Massive eruptions have occurred at Yellowstone approximately every 600,000 to 700,000 years. The last one was 640,000 years ago. t/f

true

Read the two statements that follow and select the appropriate response. Shield volcanoes are composed of rocks that form from low silica magma. Lava domes are composed of rocks with a high silica content. t/f

true

The volume of magma will increase as it rises through the crust and comes closer to Earth's surface. Select one: True False

true

Volcanic Dome

very viscous lava; relatively small; commonly occurs adjacent to craters of composite volcanoes

Which of the following are examples of data that would be useful for geologists to collect to potentially predict a volcanic eruption? (select all that apply) Learning Objective: I can list the features and processes that geologists study when trying to predict a volcanic eruption. Choices: A. seismic measurements B. gas emission measurements C. rock samples from near the volcano D. temperature measurements E. topographic measurements

a,b,d,e

What is the most common rock found in composite volcanoes?

andesite

Magma viscosity is primarily dependent upon which combination of factors? Select one: a. Water content and temperature of the magma b. Temperature and composition of magma c. Depth of magma source and gas content of magma d. Water content and pressure of the magma e. Basalt content and gas content of magma

b

hich of the following is the best description of a flood basalt? Learning Objective: I can describe the characteristics of flood basalts and how they changed the climate. Choices: A. A flood basalt is the technical term for the process that creates basalt at a mid-ocean ridge B. A flood basalt is an enormous eruption or series of eruptions of basaltic lava from a fissure that spreads out over a large area C. A flood basalt is a particularly large and violent eruption of basaltic lava that ejects large lava bombs over a wide area D. A flood basalt is a special type of eruption of basaltic lava near a water source that causes flooding of water in the surrounding area

b

The collapse of rocks overlying a depleted magma chamber is associated with the eruption of what volcanic feature?

caldera

Which type of volcano is associated with the more viscous magma?

composite

Which type of volcano is associated with the more viscous magma? Select one: a. Shield volcano b. Composite volcano

composite

Pyroclastic flows are common products of

composite volcanoes

Most active volcanoes on Earth are examples of _________ volcanoes formed in association with ____________.

composite; subduction zones