Although scientists have long been debating the history of Earth's climate changes, not much detail is actually known - something that will soon change with a new drilling system that brings up samples of lake sediment from millions of years ago.

Two scientists at the University of Arizona are part of the four-university team that will be working on the project that will drill for layered sediment samples, or cores, in east Africa's Lake Malawi - one of the deepest and oldest lakes on Earth.

The depth of drilling that the new GLAD800 system allows, together with the age of the lake, will enable scientists to learn more than ever about the history of climate change in the tropics.

"That's where it gets really exciting," said geosciences professor Andrew Cohen, one of the scientists who will be participating in the research drilling.

"(The cores) are going to provide us with that continuity of records that we don't have now," he said. "They will give us an ability to use long records of a million years or more - on an annual level."

The core samples taken out of Lake Malawi, which combined are expected to be thousands of meters long, will be analyzed layer by layer to determine climate history.

Scientists will look at the color and thickness of the sediment layers - each of which represents either a wet or dry season - as well as organic materials that may be indicators of past climates.

"The layers help us interpret what happened there at some time in the past," Cohen said. "Then, we put together a history of the events."

One of the main questions that scientists will be looking to answer with the analysis of Lake Malawi cores is whether global climate changes are driven by activity in the poles or in the tropics.

The data will be compared to data taken from polar ice cores - previously the only source of significantly old and detailed cores - to see if any information points toward which area actually leads to climate change.

The samples will also provide detailed information about the geology, ecology and anthropology of the region.

"Most records in geology look at long time intervals," said David Dettman, a geosciences senior research specialist who is also involved in the drilling project. "It's very rare to get annual layering. There are tree rings, but they don't go back as far."

This region of lakes in East Africa "is an area of fundamental importance for understanding plate tectonic processes," Cohen said. "Hopefully, we're going to learn a lot about plate tectonics and geological history."

Lake Malawi has large numbers of endemic species - species that occur naturally nowhere else. Fossilized remains of crustaceans, snails and algae in the cores will reveal a lot to ecologists about the evolution of these special communities.

"This region is the origin of human evolution, and we will be able to tell what the climates were like, in detail, during this critical time interval of evolution," he said.

The GLAD800 drilling system, which is specifically designed for use in lakes, represents a new, more affordable method of scientific drilling. Earlier drilling systems cost up to $75,000 a day to operate whereas the GLAD800 costs $3,000.

"What we're trying to achieve with the GLAD800 system is a very affordable system that can be moved from lake to lake and can be operated at a comparatively low expense," Cohen said.

The drilling, which is funded by a $2 million National Science Foundation grant, will begin in January 2003 while Lake Malawi is in its rainy season.

Syracuse University, the University of Minnesota in Duluth and the University of Rhode Island are also involved in the project.