Unified Interior Regions

As we enter the month of May, we are remiss in not remembering that April was "Tsunami Awareness Month". April was chosen as "Tsunami Awareness Month" because the deadliest tsunami to strike the Hawaiian Islands occurred on April 1, 1946. What is often overlooked is that the largest and deadliest locally generated tsunami also occurred in the month of April.
 

After an earthquake felt by residents of Hawai`i County, we at the U S Geological Survey's Hawaiian Volcano Observatory are often asked what the earthquake means or indicates in terms of the volcano's behavior. It is beyond our ability to know the detailed implications of a single earthquake event for the complex and inter-related volcanic and tectonic processes that shape our island.

At 2:56 PM local time, the Hawaiian Volcano Observatory seismographic network recorded a moderate earthquake from the Ka‘ū district of the Island of Hawai‘i.

Boaters, hikers, pilots, and other outdoor enthusiasts can use hand-held Global Positioning System (GPS) receivers to locate themselves or to navigate to a point of known position. Volcanologists routinely use hand-held GPS receivers to map lava flows and other volcanic features. 

An ancient Japanese proverb says that the most recent disaster fades from memory just before the next one strikes. Recently our friend Garret Hew of East Maui Irrigation inquired about the great 1938 Maui earthquake. That's good news; that earthquake hasn't faded from memory yet.
 

It started innocently enough. The long-lived lava lake disappeared from Halema`uma`u on February 21. Seventy-eight earthquakes were recorded in March, many along Kīlauea's east rift zone as far as 45 km (27 miles) from HVO; one on the 29th was felt in Hilo.

Earth scientists know a lot about Mauna Loa above sea level but much less about it under water. Studies have naturally focused on the easily accessible island, where one can directly observe and sample rock exposures, gauge the time between eruptions, and trace evolutionary changes in the chemical makeup of the lava flows. 

One common saying in the real estate business is that location is everything. This is particularly true from both geological and biological standpoints here in Hawaii. The Hawaiian hot spot has produced one of the most isolated island chains in the world, with some benefits not often appreciated. One of them is the natural quarantine imposed by more than 3000 km (2,000 miles) of open ocean.

Kīlauea's summit magma chamber is connected to the rift-zone vents like a water tank linked by hose to an irrigation system. The hose comprises the dikes that lie at 3-4 km depth along the trace of the rift zones. 

Among the many tools earth scientists use, the measurement of gravity variations over the earth's surface is one of the most useful for studying Hawaiian volcanoes. You're surprised to hear that gravity is not a constant?
 

Some readers will know that the largest eruption in the world during the 20th century took place in Alaska in 1912, producing the Valley of Ten Thousand Smokes near Mount Katmai (13 cubic kilometers; 3.1 cubic miles). These same readers may also know that the second largest eruption of this century formed the caldera at Mount Pinatubo, Philippines, in 1991 (5.3 cubic kilometers; 1.3 cubic miles).