The other day I heard a CNN news-reader, during the time when readers don’t read, but speak for themselves, say right after a story of the October 15th big Hawaii earthquake: “My, what a strange place for an earthquake to take place!”

So much for earth science education!

Actually we know that the Hawaiian Islands are very active geologically. Thousands of quakes occur every year in the Hawaiian Islands. Many of these are of magnitude 2.0 or less, but on Sunday, October 15, a 6.7 magnitude earthquake occurred off the Big Island, causing damage to the island, but fortunately, no loss of life.

The geology of the islands is monitored and observed at the Hawaii Volcano Observatory. The two major volcanos in Hawaii are Kilauea and Mauna Loa. Kilauea is the youngest volcano on the islands, and Mauna Loa is the largest volcano on the Earth. As I mentioned above, thousands of earthquakes occur each year, and they are integrally associated with the volcanic activity on the islands. Earthquakes and volcanos go together like peanut and jelly.

Back to earthquakes. Some earthquakes occur whenever there is a volcanic eruption. The movement of magma through the volcanos vent system disturbs the surrounding rock structure, causing quakes. Earthquakes can also occur without an eruption. Some of the large magnitude quakes on Hawaii occurr deep, near the base of the volcanos (60 miles below the surface). This typically are very strong, such at the October 15th quake. Here is a map showing earthquakes on and near the Big Island.

These are often referred to as “tectonic quakes.”
If you visit the Hawaiian Volcano Observatory, you can link to a list of recent as well a history of Hawaii earthquakes.

There are actually very few places on the earth that don’t have earthquakes. Most, of course, occur at the edges of the plate boundaries (see the map below), but they can occur in many other places, even in the middle of a crustal plate.

The large quake that occurred on Hawaii recently is rare, but when quakes of this size occur, much damage can be inflicted, as was seen on October 15.