Everything at the Membrane Domain
Famous wildlife photographer, Sebastian Copeland, utilized a graphic picture to raise awareness of human induced climate change. “‘For the state of the ice in general, we’re headed into uncharted territory. There’s no doubt about it. The frozen remains of this young bear point to starvation. The faster retreat of the sea ice, a bear’s favoured spot for seal hunting, leads to longer fasting periods and the demise of more animals from starvation.”
Part of the Human Induced Climate Change Experiment
One of the goals of the USGS Coastal and Marine Geology Program is a national assessment of coastal change hazards. Hurricanes provide a powerful force that generates dangerous waves and currents capable of moving large amounts of sand, destroying buildings and infrastructure, and reshaping our nation’s coastline. Our research focuses on understanding the magnitude and variability of the impacts of hurricanes and extreme storms on the sandy beaches of the United States. The overall objective is to improve the capability to predict coastal change that results from severe storms. Such a capability will support management of coastal infrastructure, resources, and safety.
Hurricane Sandy Example
As Hurricane Sandy moved northward along the U.S. Atlantic coast in October 2012, U.S. Geological Survey scientists worked to determine where and how the storm’s waves and surge might dramatically reshape the beaches and dunes that stand between the storm and coastal developments. Through a complex modeling process that uses coastal elevations, wave forecasts, and potential storm surge, they predicted coastal change hazards, such as shoreline and dune erosion, that might be expected during a Sandy landfall.
Using the latest storm information available, USGS predicted the likelihood of a range of coastal change impacts within the region affected by the storm:
Hurricane Sandy, the largest Atlantic hurricane on record, made landfall on October 30, 2012, and impacted a long swath of the Mid-Atlantic coastline. Many areas that had been hit by Hurricane Irene in August 2011 were again battered by strong waves and surge. The barrier islands were breached in a number of places and erosion of the beach and dunes occurred all along the Mid-Atlantic coast. This was the most destructive storm to impact this coastline since an extremely powerful nor’easter in December of 1992.
Following landfall, oblique aerial photography and lidar surveys of beach elevations were used to document the changes that occurred as a result of the storm. In addition, field measurements of the beaches and dunes were collected immediately after the storm. Comparisons of data collected before the storm show the nature, magnitude and spatial variability of the coastal response. These data will be used to further refine predictive models for storm-induced erosion.
Pre-landfall
WASHINGTON — Research by NASA and international scientists concludes giant asteroids, similar or larger than the one believed to have killed the dinosaurs, hit Earth billions of years ago with more frequency than previously thought.
To cause the dinosaur extinction, the killer asteroid that impacted Earth 65 million years ago would have been almost 6 miles (10 kilometers) in diameter. By studying ancient rocks in Australia and using computer models, researchers estimate that approximately 70 asteroids the same size or larger impacted Earth 1.8 to 3.8 billion years ago. During the same period, approximately four similarly-sized objects hit the moon.
“This work demonstrates the power of combining sophisticated computer models with physical evidence from the past, further opening an important window to Earth’s history,” said Yvonne Pendleton, director of NASA’s Lunar Science Institute (NLSI) at NASA’s Ames Research Center at Moffett Field, Calif.
Evidence for these impacts on Earth comes from thin rock layers that contain debris of nearly spherical, sand-sized droplets called spherules. These millimeter-scale clues were formerly molten droplets ejected into space within the huge plumes created by mega-impacts on Earth. The hardened droplets then fell back to Earth, creating thin but widespread sedimentary layers known as spherule beds.
The new findings are published today in the journal Nature.
“The beds speak to an intense period of bombardment of Earth,” said William Bottke principal investigator of the impact study team at the Southwest Research Institute (SwRI) in Boulder, Colo. “Their source long has been a mystery.”
The team’s findings support the theory Jupiter, Saturn, Uranus and Neptune formed in different orbits nearly 4.5 billion years ago, migrating to their current orbits about 4 billion years ago from the interplay of gravitational forces in the young solar system. This event triggered a solar system-wide bombardment of comets and asteroids called the “Late Heavy Bombardment.” In the paper, the team created a model of the ancient main asteroid belt and tracked what would have happened when the orbits of the giant planets changed. They discovered the innermost portion of the belt became destabilized and could have delivered numerous big impacts to Earth and the moon over long time periods.
At least 12 mega-impacts produced spherule beds during the so-called Archean period 2.5 to 3.7 billion years ago, a formative time for life on Earth. Ancient spherule beds are rare finds, rarer than rocks of any other age. Most of the beds have been preserved amid mud deposited on the sea floor below the reach of waves.
The impact believed to have killed the dinosaurs was the only known collision over the past half-billion years that made a spherule layer as deep as those of the Archean period. The relative abundance of the beds supports the hypothesis for many giant asteroid impacts during Earth’s early history.
The frequency of the impacts indicated in the computer models matches the number of spherule beds found in terrains with ages that are well understood. The data also hint at the possibility that the last impacts of the Late Heavy Bombardment on Earth made South Africa’s Vredefort crater and Canada’s Sudbury crater, both of which formed about 2 billion years ago.
“The Archean beds contain enough extraterrestrial material to rule out alternative sources for the spherules, such as volcanoes,” said Bruce Simonson, a geologist from Oberlin College in Oberlin, Ohio.
The research was funded by NLSI and conducted by members or associates of NLSI’s Center of Lunar Origin and Evolution, based at SwRI.
The impact study team also includes scientists from Purdue University in West Lafayette, Ind.; Charles University in Prague, Czech Republic; Observatorie de la Cote d’Azur in Nice, France; and Academia Sinica in Taipei, Taiwan.
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