By mapping the loess and the trail of rock debris left by the glaciers, scientists determined that the ice sheets had once stretched down over the familiar bowls of the Great Lakes in North America and across the British Isles and Scandinavia.
Thick glaciers, far larger than those that currently cap the mountain peaks, covered the Alps.
by Holli Riebeek · design by Robert Simmon · June 28, 2005 The first pieces of evidence for climate change came from the land itself, from the misplaced boulders scattered across much of the Northern Hemisphere, though there were other signs as well.
A homogeneous, fine yellow soil covered more than one million square miles of Europe, Asia, and North America.
In time, geologists discovered other layers of similar soil from earlier times—a sign that the climate had not changed just once, but at least three or four times.
Loess deposits, composed of fine wind-blown dust produced by the grinding action of glaciers, indicate the former presence of ice sheets in locations around the Northern Hemisphere.
The mineral deposits accumulate in the well-known icicle-shaped rock on the ceiling, a stalactite, and in a mound on the floor where the drip lands, a stalagmite.
One of the world’s largest underground chambers, the Carlsbad Cavern is resplendent in the intricate finery of the rock formations that form there.
Beyond their breath-taking beauty, the formations in Carlsbad and the more than 100 other caves in the area provide a record of rainfall in the southwestern United States.
Tucked away inside the Earth, the rocks are protected from the weathering and large-scale erosion that taints other land-based climate records.
As water runs through the ground, it picks up minerals, the most common of which is calcium carbonate.