New images produced of the ocean crust (using seismic profiles), shows that the upper crust and lower crust are formed by two different sources of magma. Researchers from Woods Hole Oceanographic Institute, Columbia University’s Lamont-Doherty Earth Observatory and the Scripps Institution of Oceanography, analyzed data from the Juan de Fuca ridge, which sits offshore of Oregon and Washington. The images are the first of their kind showing solidified magma lenses and sills, narrow lateral intrusions of magma, embedded in the boundary between the mantle and the overlying crust, a region known as the Moho transition zone. The existence of these magma lenses near a mid-ocean ridge suggests that the lower oceanic crust is formed from several smaller sources of magma rather than a single large pool located in the middle of the crust. The study appears in the current issue of Nature.
Researchers at the National Center for Atmospheric Research have ran a computer simulation that shows that rising levels of carbon dioxide 250 million years ago contributed to a 90 degree increase (over today’s temperatures) and was responsible for the largest mass extinction even in Earth’s history. Their computer simulation shows rising atmospheric levels of carbon dioxide interfered with the oceans` oxygen circulation, raising temperatures by nearly 90 degrees Fahrenheit above today`s temperatures. The researchers said the global warming extinguished an estimated 95 percent of all marine life and about 70 percent of all land species. The research appears in the September issue of Geology. More information at Science Daily as well. Press release is here.
Hurricane Katrina is currently moving towards New Orleans and expected to make landfall on Monday night as either a category 4 or 5 storm. Due to the extensive network of levees that protect the city from the Mississippi River, major flooding is expected. Here is an older article that discussed scenarios for New Orleans if it was ever hit by a major hurricane. People have known for centuries that New Orleans is a risky spot — the biggest river in North America wraps around it; and most of the land is below sea level. But researchers say they’ve been learning just how grave the problem is, only in the last few years. And they say the city and the nation aren’t prepared to handle it. To begin to understand why, we clamber up the levees along the Mississippi River. Our guide is Oliver Houck, who runs the environment program at Tulane University Law School. Houck describes it, “There’s no place in the world that has a levee system that is as extensive as this one—it’s a monster system.”
Waves from tsunami generated during the Sumatra Earthquake last December reached around the world. Analysis of data recorded by tidal gauges and satellites shows that the wave traveled around the world several time and that characteristics of the ocean floor caused some locations far away from the epicenter to experience higher waves than places located closer to the epicenter. Wave heights recorded at Callao, Peru, 11,400 miles east of the epicenter of the quake that caused the wave, and at Halifax, Nova Scotia, 14,400 miles west, were higher than at the Cocos Islands, located just over 1,000 miles south of the quake, the team noted. The unusually high waves so far from the quake site result from two factors, the main east-west direction of the wave’s energy and the focusing mechanism of the deep-sea ridges, Titov’s team reported. The first tsunami wave arriving at the Cocos Islands peaked at about 12 inches, the team said. By contrast, waves arriving at Callao and Halifax topped 20 inches, the team reported.
A new study by geologists at the University of Illinois at Urbana-Champaign shows that the Earth’s core rotates at a faster rate than the Earth’s surface, confirming suspiciouns scientists have had for a long time. The solid inner core has an uneven consistency, with some parts denser than others, and this can either speed up or slow down shock waves from earthquakes as they pass through. So the researchers speculated that if the Earth’s inner core is rotating faster than the rest of the planet, then shock waves from waveform doublets would enter and exit through different parts of the core despite originating from roughly the same spot on the planet’s surface.