Ice age hit Missouri 2.4 million years ago.Analyses of soil from central Missouri have pinpointed just when North America's most recent spate of ice ages began: 2.4 million years ago. When the high-energy, extraterrestrial particles known as cosmic rays cosmic rays, charged particles moving at nearly the speed of light reaching the earth from outer space. Primary cosmic rays consist mostly of protons (nuclei of hydrogen atoms), some alpha particles (helium nuclei), and lesser amounts of nuclei of carbon, nitrogen, strike crystals of quartz, they often produce radioactive atoms of beryllium beryllium (bərĭl`ēəm) [from beryl ], metallic chemical element; symbol Be; at. no. 4; at. wt. 9.01218; m.p. about 1,278°C;; b.p. 2,970°C; (estimated); sp. gr. 1.85 at 20°C;; valence +2. and aluminum. Therefore, the presence of beryllium-10 and aluminum-26 is a sign that the quartz has spent time near Earth's surface Noun 1. Earth's surface - the outermost level of the land or sea; "earthquakes originate far below the surface"; "three quarters of the Earth's surface is covered by water" surface , says Charles W. Rovey II, a geologist at Southwest Missouri State University Missouri State University is a state university located in Springfield, Missouri. It is the state's second largest university in student enrollment, second only to the University of Missouri. From 1972 to 2005, Missouri State was known as Southwest Missouri State University. in Springfield. If that material is later covered with deep layers of sediment that protect it from new cosmic ray cosmic ray High-speed particle (atomic nucleus or electron) that travels through the Milky Way Galaxy. Some cosmic rays originate from the Sun, but most come from outside the solar system. bombardments, the slow decay of those radioactive isotopes serves as a ticking clock that can reveal when the material was buried. Rovey and his colleagues analyzed a sample of soil from deep in a clay pit near Danville, about 110 kilometers west of" St. Louis. The ratio of beryllium-10 and aluminum-26 in that sample indicates that the 7.5-meter-thick layer of glacial debris atop the soil layer was deposited about 2.4 million years ago. This is the most direct evidence yet for the start of the ice age. Previously, scientists only had inferred, from isotopes in marine sediments, that large-scale glaciation in North America occurred at that time. The researchers report their findings in the Jan. 14, Science.--S.P. |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion