Ah, disaster: it’s so much fun. I’ve long had an interest in geology, and that led in turn to related areas, such as glaciology, paleoclimatology, and the like.

Vredefort dome, South Africa
Space shuttle image STS51I-33-56AA

I just watched the movie, The Day After Tomorrow, and following that I was browsing the net, checking out what has been found in the attempt to piece together the transition from the last ice age to this most recent of interregnums, our warm period, the Holocene. And of course one finds on the net plenty of scientific information, but also a plethora of wacky obssession with doomsday scenarios. It’s a curious propensity, this fascination with events approaching from the periphery of human consciousness and memory. Shadows from beneath the bed.

The biggest local cosmic train wreck so far? The Vredefort dome.

Where else would one find descriptions as colorful as this (from the link above):

This ring of hills comprises quartz conglomerates as found in the gold-bearing strata of the Witwatersrand reefs.

Village, Vredefort dome, South Africa

Village stones, Vredefort dome, South Africa

Photos from
Hartebeesthoek Radio Astronomy Observatory

The white quartz pebbles are evident. This was once the bed of a fast flowing water course which
deposited grains of quartz and the pebbles. This area was mined for gold in the 1880’s. However the concentration of gold was much poorer than at Johannesburg, and the diggings were soon abandoned. Old mine adits are still to be seen in the hills. This is the Amazon Reef.

The outermost ring of hills was home to a quite different group of people in the 1500’s to 1700’s. These were SeSotho/SeTswana-speaking farmers. This village at Askoppies was a defensive position on the crest of the hill, but it did not save the village from destruction, by the warriors of Mzilikazi. The view shown above left looks east, back in towards the inner rings of the Vredefort dome.

The stone walls of the village are shown above right. They are made of the fine-grained grey Ventersdorp lavas that comprise this ridge. These rocks are 2700 million years old.

of illustrative climate-change related charts is here (I’ll try to include attributions later, but most are from the excellent American Scientist article cited in the graph caption, below).

My favorite of these? The chart that shows anthropogenic induced change in the atmospheric concentration of C02. The two graphs shown are derived from an ice core from Vostok, Antarctica. The top chart is of deuterium, a proxy for temperature. The bottom is of CO2, parts per million. The time scale at the bottom is in thousands of years before the present.

Vostok Ice Core, Antarctica, 0 to 160,000 years before present
Top chart is deuterium (per mil).
Bottom chart is C02 (parts per million by volume).

Graphic from “Rapid Climate Change,” Kendrick Taylor,
American Scientist, July-August, 1999.

The Holocene is the 10,000 or so year-long warm period that we’re living in now. The cold stretch of 125,000 years prior to the Holocene is the most recent Pleistocene era glaciation, know as the Wisconsin ice age in North America. Just before the Wisconsinin is the Eemian, another brief warm spell like our own; and before that lies an earlier glacial period (but still lying within the 2 million year extent of the Pleistocene). The red spike on the left side, bottom chart is the increase in atmospheric C02 caused by humans in the industrial era, now 150 years old.

This entry was posted on Tuesday, March 1st, 2005 at 3:14 pm and is filed under Climate Change, Ecology, General, Geology, Paleoclimatology, Science. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.