19 August 2007

Pillow lavas deepen undertanding of UAE history

July 28 - August 10, 2007
Issue 28

Pillow lavas are the most common rocks on earth – you just do not see them because they form underwater, appearing only on the surface of the sediments. But when Dr. Benjamin R. Jordan, Assistant Professor at the Department of Geology of the College of Science explored the east side of Al Ain, he found out something that could re-shape the country's history.

"The rocks east of Al Ain are a unique geologic feature. There are only three areas in the world where the type of pillow lava found here has been identified. What is unusual about the ones here is that they formed within the sediments themselves, rather than on the surface of the sediments. Geologically, it is interesting and it is unique, for it was not known before, or had not been studied in detail," he explained.

"Some of the pillows formed within the sediments and some formed below and they overlap. Usually molten rock on the surface of the Earth is called lava and when it is below the surface it is called magma. Here we have an underground feature formed by magma that looks like a surface feature formed by lava."

But if this occurs, does that mean that there are still eruptions underground? "Not here. Maybe in [other] areas of the ocean today, but these probably formed in a usual situation or environment. It appears that the eruption was a small one, with just enough magma to make a few pillow lavas and then stop. If it had been a big eruption, the sediments would have been completely overwhelmed by the magma and lava and we would not have any evidence of the pillow structures that formed underground. They would have been obliterated. The eruption had to be small and the sediments would have had to have been very, very wet so that the magma cooled quickly and behaved like lava does that erupts into open water."

"There is evidence that there were seamounts or underwater volcanoes in this area. It is likely that this eruption was from a larger underwater volcano. Part of the evidence for that is that, in some cases, there are blocks of intact limestone that are also within the same layers of sediments as the pillow lavas. Limestone is formed in shallow water. Coral reefs are an example of one way they form."

"Some researchers theorize that there were seamounts that built up a structure that reached close to the surface where limestone could form and coral could grow. From time to time, blocks of limestone or reef would break off in an underwater landslide and sink into deep water where they would be buried by the same sediments that the pillow lavas formed in. These blocks indicate that there were seamounts in the area near where the pillow lavas formed and are probably associated with them."

"From all of this we can see that there was a lot going on in the geologic past in this area. The main benefit of this research is that we can add to the history of what was happening in this area in the past. We can answer questions such as why are the mountains here, why is there limestone here, and how did the pillow lavas form. By doing this we can know what was happening millions of years ago to make the land of the UAE what it is today."

No comments: