erth 353 geologic hazards midterm

According to the World Meteorological Organization, every dollar that is invested in disaster preparedness can prevent ________ in economic losses related to disasters.

seven dollars

What stage of disaster relief usually lasts for the longest periods of time?

Restoration

What is the risk of a natural hazard?

The total danger a community faces from an event occurring

Based on what you learned from the U.S. Geological Survey Earthquake Map, approximately how many earthquakes occur in the U.S. every week?

1,000 to 2,000

Based on what you learned from the Smithsonian/U.S. Geological Survey Weekly Volcanic Activity Report website, how many volcanoes are usually erupting worldwide? 

about 20

Which of tectonic features are associated with volcanic activity?

mid-ocean ridges, continental rifts, subduction zones, and hotspots/mantle plumes

Which type of magmas (or lavas) have the highest silica (SiO₂) content?

felsic

What term is used to describe the relative ability of a substance to flow?

viscosity

Which compound is most important in determining the viscosity of lava?

Silica (SiO₂)

Volcanic eruptions are measured using the following scale:

Volcanic Explosivity Index

Sudden melting of glaciers on volcanoes can generate which hazards?

lahars

A pyroclastic flow can best be described as:

a flow of hot volcanic gas and ash

What process is responsible for producing most of the world’s earthquakes?

Displacement and motion along a new or pre-existing fault

As the magnitude number of an earthquake increases by 1 (for example, from 5 to 6), there is an increase in the amount of energy released by a factor of:

32

Most earthquakes occur:

Along plate boundaries

The term epicenter refers to:

The location on the surface of the Earth, directly above where movement occurs and where seismic waves are generated.

Which of the following measures an earthquake's intensity based on the observed effects on people and structures?

the Mercalli scale

In all cases, tsunami waves are caused by:

Sudden displacement of water

What type of plate boundaries generate the most tsunamis?

subduction zones

In deep water, tsunamis move at _____________. When they reach shallow water in coastal areas, the tsunami _____________ and ____________ in height.

fast speeds, slows down, increases

There is evidence for very large tsunamis generated by ancient submarine landslides in Hawaii. How high above sea level are deposits from these tsunamis found?

300 meters (about 1,000 feet)

A large asteroid impact like the one that created the Chicxulub crater would generate a mega-tsunami with waves that are __________ high.

1.5 km (about 1 mile)