Geology topics
Research about Island of Hawaii
Source-linked reports with geographic coverage including Island of Hawaii.
Hawaiian Volcano Observatory; summary 93, part I; seismic data, January to December 1993
No abstract available.
The geohydrologic setting of Pololu stream, Island of Hawaii, Hawaii
Streamflow measurements indicate that Pololu Stream, which is on the northeastern side of Kohala Volcano, is intermittent, although the stream has previously been interpreted as perennial. The main channel of the stream does not gain water from ground-water sources except at a wetland and shallow pond at the terminus of the stream channel. Ground water in the area is found as high-level dike-impounded ground water in the higher altitudes, as basal ground water in the form of a freshwater lens at lower altitudes, and as perched ground water lying above dike-impounded ground water or the freshwater lens. The water tables of the dike-impounded ground water and the basal ground water are below the altitude of the streambed of Pololu Stream and its tributaries except near the ocean at the wetland and pond area. Two of the three tributaries to the stream are perennial, fed by springs that are possibly perched. These tributaries lose water in their lower reaches and go dry before joining Pololu Stream. The third tributary has flow from a leaking flume in Kohala Ditch; the flow reaches Pololu Stream, flows for about 4,000 feet, then is lost in the lower reaches of the stream. Streamflow is affected by geology. Where the streambed is composed of a single thick volcanic lava flow, streamflow is maintained, whereas farther downstream streamflow disappears where the streambed is composed of alluvium. The pond and wetland at the terminus of the stream channel are where the land surface intersects the basal ground-water body. Although the pond is perennial, conditions at the pond can be highly variable. During dry periods, seepage and wave overwash from the ocean, small amounts of rainfall, and springs add water to the pond. During high rainfall, the lower reach of Pololu Stream flows, the lower valley floods, the beach berm erodes, and the pond is transformed into a stream outlet to the ocean.
Living on active volcanoes - The Island of Hawai'i
People on the Island of Hawai'i face many hazards that come with living on or near active volcanoes. These include lava flows, explosive eruptions, volcanic smog, damaging earthquakes, and tsunamis (giant seawaves). As the population of the island grows, the task of reducing the risk from volcano hazards becomes increasingly difficult. To help protect lives and property, U.S. Geological Survey (USGS) scientists at the Hawaiian Volcano Observatory closely monitor and study Hawai'i's volcanoes and issue timely warnings of hazardous activity.
Volcanic gases create air pollution on the Island of Hawai’i
In a handful of molten magma weighing about a pound, there is less than a tenth of an ounce, by weight, of idssolved gas-roughly the same weight as a pinch of table salt. Yet this tiny amount of gas produces spectacular lava foundations hundreds of meters high (see accompanying photograph). The fountain occurs as magma reaches the surface, because dissolved volcanic gases exolve and expand tremendously as pressure on the magma is released. Anyone who has shaken a bottle of soda and opened it quickly has received the full value of this basic principle of physics. Gases are dissolved in magma at depth, where pressures within Earth's crust are very great-many thousands of pounds per square inch. As the magma rises to the surface and erupts, the pressure decreases, and gas is released. The main gases dissolved in magma are water vapor, carbon dioxide, and sulfur gases, with lesser amounts of others, such as hydrogen, carbon monoxide, hydrochloric acid, and hydrofluoric acid. In our pinch-of-salt-to-a-handful-of-magma illustration above, most of the "pinch" is water vapor, followed by lesser amounts of carbon dioxide and sulfur gases with a few "grains" of hydrogen and other acid gases. The current eruption of Kilauea produces large quantities of volcanic gases that contribute to "volcanic air pollution." In this article we discuss the nature of the gases released from Kilauea, hoe we study them, and what happened to the gases in the environment after they are released.
Morphology of the island of Hawaii
Digital elevation data for the island of Hawaii from the U.S. Geographical Survey gridded at 30 m spacing was used to generate a slope map, a shaded relief map, and plots that compare slope and elevation for each of the five volcanoes that compose the island.These computer- generated products are useful in analyzing the morphology of the sland. The volcanoes become steeper with increasing age. The five volcanoes, in order of increasing age, are Kilauea, Mauna Lao, Hualalai, Mauna Kea and Kohala; their average slopes are 3.3, 5.4, 6.6, 7.0, and 11.3, respectively. This relation apparently results from growth of the late, steeper alkali cap on the older volcanoes that include more viscous, thicker flows, flows that are smaller hence tend to pile up more near the summit vents, and volatile- rich lavas that commonly produce steep sided cinder cones at summit vents. The cause of the gentler slopes of younger volcanoes include the high proportion of exposed fluid lava flows from the shield building stage, the ponding of lava against earlier volcanoes, and the grading of lava to sea level; subsidence of the older volcanoes have cause these gently dipping near-seas-level lava flows to subside below the sea. Finally, steep erosional canyons have developed in large areas of the older volcanoes (notably Kohala). Virtually all of the major fault systems on the sland appear to be related to the upper parts of giant landslides, most of which are hidden below sea level on the submarine flanks of the volcanoes. These are generally normal faults in the tensional regime at the heads and upper parts of the landslides Subtle changes in slope hint at buried landslide related faults scarps that have been covered by subsequent lava flows. Major erosional canyons are present in only two places, each presumed to be in the amphitheaters of the major landslides. The probably formed in this setting because steam erosion is favored by the steep sloped generated at the heads of landslides. The slope map clearly displays two bands of steep slope on Mauna Kea that mark the terminal moraines at the edges of the last two advances of the Pleistocene ice cap.
Earthquakes and related catastrophic events, Island of Hawaii, November 29, 1975: A preliminary report
The largest earthquake in over a century--magnitude 7.2 on the Richter Scale--struck Hawaii the morning of November 29, 1975, at 0448. It was centered about 5 km beneath the Kalapana area on the southeastern coast of the island at 19° 20.1 ' N., long 155° 01.4 ' W.). The earthquake was preceded by numerous foreshocks, the largest of which was a 5.7-magnitude jolt at 0336 the same morning, and was accompanied, or closely followed, by a tsunami seismic sea wave), massive ground movements, hundreds of aftershocks, and a volcanic eruption. The tsunami reached a height of 12.2-14.6 m above sea level on the southeastern coast about 25 km west of the earthquake center, elsewhere generally 8 m or less. The south flank of Kilauea Volcano, which forms the southeastern part of the island, was deformed by dislocations along old and new faults along a 25-km long zone. Downward and seaward fault displacements resulted in widespread subsidence, locally as much as 3.5 m, leaving coconut palms standing in the sea and nearly submerging a small, near-shore island. A brief, small-volume volcanic eruption, triggered by the earthquake and associated ground movements occurred at Kilauea's summit about three-quarters of an hour later. The earthquake, together with the tsunami it generated, locally caused severe property damage in the southeastern part of the island; the tsunami also caused two deaths. Damage from the earthquake and related catastrophic events is estimated by the Hawaii Civil Defense Agency at about $4.1 million. The 1975 Kalapana earthquake and accompanying events represent the latest events in a recurring pattern of behavior for Kilauea. A large earthquake of about the same magnitude, tsunami, subsidence, and eruption occurred at Kilauea in 1868, and a less powerful earthquake and similar related processes are believed to have occurred in 1823. Indeed, the geologic evidence suggests that such events have been repeated many times in Kilauea's past and will continue. The 1975 events serve as a critical, though tragic, reminder of the dynamic nature of the volcano and point up the need for careful land-use planning and adequate building codes to minimize damage and loss of life from similar events in the future. Detailed scientific study of the cause and effects of the November 29, 1975, event will take many months. This report summarizes information available in February 1976.
The 7.2 magnitude earthquake, November 1975, Island of Hawaii
The largest earthquake in over a century struck Hawaii the morning of November 29, 1975, at 4:48 AM HST. The earthquake was of magnitude 7.2 on the Richter scale. It was centered about 5 km beneath the Kalapana area on the southeastern coast of Hawaii, the largest island of the Hawaiian chain (Fig. 1) and was preceded by numerous foreshocks. The event was accompanied, or followed shortly, by a tsunami, large-scale ground movemtns, hundreds of aftershocks, an eruption in the summit caldera of Kilauea Volcano. The earthquake and the tsunami it generated produced about 4.1 million dollars in property damage, and the tsumani caused two deaths. Although we have some preliminary findings about the cause and effects of the earthquake, detailed scientific investigations will take many more months to complete. This article is condensed from a recent preliminary report (Tillings an others 1976)