Science: HOW THE ICE AGE BEGAN – from TIME Monday, March 24, 1975
Our thanks to Mr. G. Nicholas from Dallas, Texas for reminding us of this very pertinent article from 35 years ago:
“About 2 million years ago, the earth’s climate began to undergo drastic changes. The polar icecaps increased dramatically in size. Glaciers spread as far south as present-day New York City. Seeking to escape the chilly weather sweeping the face of the earth, many animals—including man—sought refuge in more southerly latitudes. Less adaptable or mobile creatures were destroyed by the advancing freeze.
Though this scenario for the beginning of the ice age has been well documented by fossil records, scientists have long been uncertain about what caused the cooling. Now, after studying cylindrical-core samples of ocean sediment dug up by the deep-sea drilling ship Glomar Challenger, two University of Rhode Island researchers have found evidence that may help provide the answer. The telltale position of layers of volcanic ash found in the cores by Geologists James Kennett and Robert Thunell suggests that the first great ice age could have been set off by a worldwide series of volcanic eruptions.
Krakatoa’s Activity. Even a single major volcanic outburst adds so much dust to the atmosphere that it reduces the amount of sunlight reaching the earth’s surface; the result can be a brief but noticeable cooling of global climate. After the eruption of Krakatoa in 1883, for instance, unusually cool weather was reported in many parts of the world for several years. The evidence is still preserved in the annual growth rings of old trees. Only recently, scientists at the University of Arizona’s tree-ring laboratory discovered disturbed rings in California trees, dating back to 1884, that showed the trees had experienced a hard freeze that year. The scientists strongly suspect that the unusually cold California weather was linked to Krakatoa’s eruption a year earlier.
It seems clear that the layers of ash in the Glomar Challenger’s cores are the residue of more than one volcanic eruption. Kennett and Thunell point out that the ash is so widely distributed, ranging from the arcs of volcanic islands in the Pacific to volcanically active regions in Central America and the mid-Atlantic, that it can best be explained by a sharp and worldwide increase in volcanic activity.
The geologists can only guess what stirred up the wide-ranging eruptions. Possibly, they resulted from a sudden increase in plate tectonic activity—the process in which the great plates that form the earth’s surface bump, jostle and sometimes slide underneath each other, carrying the continents along with them. This activity often arouses the earth’s volcanoes, most of which lie near plate boundaries. The core evidence discovered by Kennett and Thunell has given further weight to a viewpoint shared by an increasing number of scientists: that all major changes occurring in or above the earth—including variations in climate—are closely interrelated and must always be considered as part of a chain of global events.”
