The Dryas is a wildflower that grows in cooler climates. An evergreen that colonizes areas by spreading along the ground, it is found in Alaska, the Canadian Rockies and reaching as far south as Colorado.
The Younger-Dryas is also an era named for glaciation and cooler temperatures, roughly ending 11,000 years ago. The most recent major ice age started around 115,000 years ago and encompasses the extinction of the Neanderthals and the rise of man. This major glaciation was coasting towards warmer temperatures up to a sudden temperature retreat around 13,000 years ago called the Younger-Dryas and lasting around 1,500 years.
Scientists cannot put an exact year on the peak of and ice-age or the transition from a warm period to a cool period. In years, the transition is much slower, and all changes feature starts, stops, retreats and retrenching, much like a stock market chart. But we do know that the period of glaciation was severe for North America and Scotland. Scottish historians tell us that there were five or six peaks of glaciation in northern Scotland over the last 750,000 years.
Northern Europe and northern North America suffered thick glaciers two miles thick during these ice ages. Geologists tell us that Chicago, New York, most of Scotland, Finland, Norway, and the ice was thinner but still substantial in northern France, Germany and Poland. The European ice sheet appears to have receded a thousand years earlier than in Russia and North America.
Heavy rains in the deserts of North America produced lakes, including Lake Bonneville. The Great Salt Lake is a remnant of the climate of the last ice age. Even the Amazon was affected by global cooling, the jungles today were in some places a grassland more like Africa than central South America. Sea levels were also affected severely by the end of the last ice age.
As the Younger-Dryas came to and and, the seas saw a nearly 200 foot rise in sea level during the next 5,000 years. The deepest recessions of sea level in the last major ice age exceeded 400 feet below today’s sea level. For reference, the deepest part of the Chunnel is 250 feet below sea level, which is also the narrowest part of the English Channel. During the Younger-Dryas and during much of the last major glaciation period, the English Channel was probably dry, or a salt marsh, which was crossed by Neanderthal and Early humans. But the climate of southern England would have been cooler, with ice near to the north supporting small populations of early hunters and gatherers.
The extremes of sea levels had interesting effects for the Phillippines. Today’s mass of thousands of islands were one large island. It may have been possible to walk on dry land from Japan to Australia, crossing ridges exposed by the lower sea levels to Taiwan, then to the Phillippines, next to New Guinea and right onto the Australian continent. The sea level changes mean that eons of history for humanity that fished the oceans has been buried under hundreds of feet of salt water. But other differences in the environment were also prevalent.
One feature of the last ice age was air pollution. The same ice age that produced heavy rains and lakes in the deserts of North America expanded deserts elsewhere. Blowing sands and dust were up to 50 times higher during the ice age, which further blocked sun light that could have warmed the Earth.