June 13 (Reuters) - A strong 6.8 magnitude earthquake hit Guatemala on Wednesday, the U.S. Geological Survey said, and some buildings were evacuated in the capital.

Here are some key facts about the "Pacific Ring of Fire":

WHAT IS IT?

-- The Ring of Fire is a horseshoe-shaped band of volcanoes and fault lines circling the edges of the Pacific Ocean.

-- Some 25,000 miles (40,000 km) long, it runs from Chile, northward along the South American coast through Central America, Mexico, the west coast of the United States and the southern part of Alaska, through the Aleutian Islands to Japan, the Philippines and Indonesia before curving back to New Guinea, the southwest Pacific islands and New Zealand.

-- Its seismic activity results from collisions between tectonic plates.

KEY FIGURES:

-- Of the world's 1,500 active volcanoes, almost 90 percent are in the Ring of Fire.

-- Ninety percent of the world's earthquakes and 81 percent of the world's largest earthquakes occur within it.

RECENT MAJOR ACTIVITY:

-- Jan. 13, 2007, EAST OF THE KURIL ISLANDS: 8.1 magnitude

-- Jan. 21, MOLUCCA SEA: 7.5 magnitude

-- Jan. 30, WEST OF MACQUARIE ISLAND: 6.8 magnitude

-- March 25, VANUATU: 7.1 magnitude

-- April 1, SOLOMON ISLANDS: At least three people are reported to have died after an 8.1 magnitude earthquake in the Pacific Ocean.

Sources: Reuters, USGS

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