By John Barwis Holland Sentinel contributor Posted Feb 04, 2010 @ 10:13 AM Park Township, MI — Anyone who sees a sonogram of an unborn child can imagine the thrill experienced more than 100 years ago by the first physicians to image internal organs using x-rays. The joy and amazement of lifting the veil on previously unseen wonders has driven the lure of discovery since man’s very beginning. Over the past 40 years earth scientists have perfected 3D seismic tools, similar to sonograms but employing more powerful energy sources, which illuminate details of the ground beneath us to a depth of several miles. Seismic surveys covering areas totaling millions of square miles provide exquisitely detailed images of the rocks that record Earth’s history. Seismic data reveal the shape of the tropical sea and coral reefs that was Michigan during the Devonian Period more than 350 million years ago. An unexpected benefit of excellent subsurface images is our ability to document the history of sea level. The architecture of buried sediments reveals ancient rivers, deltas, beaches, continental shelves, coral reefs, submarine fans and other features. Falling sea-level events are evidenced by certain erosional features, while rapid rises in sea level are recorded by marine layers lying on sediments once at or above sea level. By combining these observations with outcrop studies, geologists have been able to document several hundred major sea-level cycles during the past 542 million years, ranging in magnitude from tens of feet to more than 400 feet. An even larger number of smaller events have been recorded. What caused these changes during a period in which modern man and his CO2 emissions did not exist for the first 541.8 million years? Some evidence suggests that longer-term rises (millions to tens of millions of years) may be due to movements of the Earth’s tectonic plates. But many studies have definitively linked more frequent sea-level cycles to climate changes caused by regular fluctuations in the amount of solar energy received by the Earth. Astronomers have shown that the shape of the Earth’s orbit varies regularly, as do the tilt and wobble of its axis. These influences result in climate cycles of approximately (in thousands of years): 400, 100, 41 and 19. Many examples of the deposits left by these cycles have been documented in the rock record, particularly the 19,000-year cycle. Such profound changes cannot be understood, or even observed, unless a scientist considers “deep time” — far longer periods than man’s written historical records, or such proxies as tree rings.