Fact or Fiction: Earthquakes

By: Staff

About 10,000 earthquakes occur every year around the globe.

According to the National Earthquake Information Center, about 1.4 million earthquakes happen annually. The large majority are microquakes, with a magnitude of 3.0 or less.

Seismologists developed the theory of plate tectonics in the mid-19th century.

Scientists had been studying phenomena like volcanoes and earthquakes for years and finally broke through with the theory of plate tectonics in the mid-20th century.

Earthquakes kill about 20,000 people a year.

The number is actually closer to 8,000 a year.

If two plates move away from each other, it creates a huge crevasse -- like the Grand Canyon.

When two plates move away from each other, magma (molten rock) seeps up through the crack.

Normal, thrust and strike-slip are some of the main types of faults.

Yep, those are some of the commonly occurring types of faults, and all of them can cause trouble.

Earthquakes happen only along plate boundaries.

It's definitely more common for an earthquake to occur along plate boundaries, but they can sometimes happen in the middle.

Scientists worry that a major quake in a megacity (population more than 8 million) could kill 3 million people.

Yes, there is concern that a good number of major cities -- many of which lie in earthquake-prone areas -- aren't ready for a major quake.

The largest earthquake ever measured had a magnitude of 9.9.

The biggest was 9.5, in Valdivia, Chile, in 1960.

A quake is considered major when it registers more than 7.0 in magnitude.

An even 7.0 is the cutoff for a major quake, and according to the U.S. Geological Survey, an average of 18 major quakes strike the world every year. There is generally one great earthquake (more than 8.0) each year.

The 1906 San Francisco earthquake was before the time of the Richter scale, but it was probably about an 8.1.

The city of San Francisco shook for a full minute on April 18, 1906. Most estimates put the quake at a magnitude of 7.8.

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About This Quiz

Earthquakes, like volcanoes, happen all the time -- but most of them are so minor we can't even feel them. They're also similar to volcanoes in that we can't fully predict them, and scientists are always waiting for the next big one to occur.

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