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Volcanic rocks give hint of Saipan’s distant past
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Posted on Apr 14 2006
A visiting geologist found some volcanic rocks in Talafofo area that tend to prove Saipan used to be a volcano millions of years ago.
Bill Burton, of the U.S. Geological Survey in Reston, Virginia, told the Saipan Tribune that he found the volcanic rocks on the surface of a very rugged area in Talafofo.
Burton said he is going to study the recovered volcanic rocks and analyze them to determine their composition and type.
“These [rocks] will help us reconstruct the history of the volcano that used to be here on Saipan…underneath Saipan,” he explained.
Burton said many people say that Mt. Tapochao could be the top of the volcano, but he disagrees with this, based on the rocks found on the mountain.
“What happened was that the island was uplifted. Well, in the beginning it was an old volcano or a series of volcanoes, then it or they stopped erupting and were eroded away. Then limestones were laid down,” he said.
Pointing at a 1956 geological map of Saipan, Burton said the blue colors are limestones that were laid down when the island was uplifted.
“So the island was coming up for the last…30 million years or something since the volcano’s eruption,” he said.
Burton and another geologist, David Weary, are on island to revise and update Saipan’s old geologic map, the latest of which was made by the USGS back in 1956. They are also on island to assist the Water Task Force and the Commonwealth Utilities Corp. in locating new sources for groundwater.
The two geologists earlier told the Saipan Tribune that they found sandstone rocks at the lookout in Kagman. They explained that sandstones tend to hold a lot of water.
“So wherever these rocks [sandstones] are found on the island, that might be a place where it is holding groundwater. So we want to make sure we understand the rock type,” Burton said.
