William Atkins
Saturday, 26 April 2008 22:39
Science -
Climate
Page 2 of 3
Rainfall that has fallen in the past, throughout the history of Earth, is well preserved within volcanic glass. This ability to retain a record of water occurs because when volcanoes erupt, particles of extremely hot molten rock are violently flung out into the air.
They hit the atmosphere and quickly cool—so fast do they cool that they almost instantaneous freeze into glass—what is called volcanic glass.
The volcanic glass has an amorphous (unstructured) internal appearance, as opposed to minerals, which have an ordered crystalline structure. Its unstructured state allows tiny holes (crevasses) to develop inside, which permits water to seep in and to be stored.
Once the glass becomes full of water (fully hydrated), it basically stops changing isotopically (that is, its chemical composition does not change).
Mulch states,
"It takes probably a hundred to a thousand years or so for these glasses to fully hydrate.” [Stanford] However, when dealing with millions of years, such small time frames allow researchers, such as Mulch, to better estimate the uplift of mountains.
The volcanic glass studied by the Mulch team had a range of being deposited on the Earth from 600,000 years to over twelve million years. This time period occurred during massive upheavals of the tectonic plates (segments of the Earth's crust that slowly move relative to each other over time) throughout the interior of the Earth.
Mulch stated,
"For the first time, we were able to document that we can track the [development of the] rain shadow on both sides of the mountain range over very long time scales." [Stanford]
Mulch's paper was published online in a scientific journal. Please read on for more details of the paper.
