The isotasy of Hawaii

Author:

Wilson, R.M.

Title:

The isotasy of Hawaii

Periodical:

The Volcano Letter

Year:

1928

Volume:

192

Pages:

1

Subject:

Gravity and mass Hawaii Island

Summary:

The objective of the investigation outlined in this document was to discover the density and bulk of the island mass of the island of Hawaii where the use of gravity observations has developed some interesting conceptions as to the state of isostatic adjustment on the island. This paper briefly outlines the method of computing theoretical gravity and the investigation lead the author to wonder how the variations of density are distributed in the isostatically adjusted earth crust. In addition, since the author believes that the island of Hawaii is, for the most part, not compensated, this begs the question, "How large may an uncompensated topographic mass be and still be upheld by this crust?" Figures show that the island is resting on the ocean floor with a pressure amounting to 9,700 pounds per square inch over an area of about 19,000 square miles. As a result, it is suggested that this load is about the greatest that can be supported simply by the strength of the earth's crust which forms the ocean floor. This has led the author to believe that the island of Hawaii is gradually adjusting by gradual sinking and downfaulting as is happening in Puna and Kona, as well as perhaps Hamakua and northeast Kohala. This may also explain the general and progressive diminishing elevation of the Hawaiian islands as a group toward the northwest that might have once been as high as the island of Hawaii. However, in an extreme case, this investigation may suggest that if the island of Hawaii is supported solely by the earth's crust that has no strength beneath it that perhaps the island as a whole would settle downwards by 11,000 feet to accomplish total isostatic adjustment. This would leave the leave the tops of Mauna Kea and Mauna Loa projecting above the ocean with summit elevations of 2,800 and 2,600 above sea level. However, it is presumed that isostatic adjustment has already been accomplished as it is known that the earth's crust has considerable strength. As a result, it is suggested that perhaps a sinking of only 8,200 feet should be taken as an estimate.

Label:

Geology

Date:

August 30, 1928

Collection:

Periodicals