Photographer : Menashe Davidson Summary Author : Menashe Davidson Pebbles are individual rock fragments that have broken off a larger piece of rock -- they come in various shapes, colors and textures. They're mostly smooth, based on how frequently they've scraped against other pebbles and rocks and how many episodes of fast flowing water they've been subjected to. Tools made from pebbles were among the earliest known artifacts . With Israel's Mediterranean climate , winter rains cause streams to flow very quickly for a limited time.
Annual Lightning Flash Rate Map Description Before scientists had satellites to detect and measure lightning frequency, it was thought that there were globally 100 lightning flashes per second, an estimate that dates back to 1925. With satellites monitoring lightning frequency, it is now accepted that the global lightning flash frequency is on the order of 40 flashes per second. NASA has two different sensors that measuring flash frequency, the Optical Transient Detector, OTD, and the Lightning Imaging Sensor, LIS.
Climate Change, Deforestation, Biomes and Ocean Currents, Plankton, Endangered Species - Earth Web SiteClick for more detail Thermohaline Change Evidence is growing that the thermohaline current may be slowed or stopped by cold fresh water inputs to the Arctic and North Atlantic oceans. This could occur if global warming is sufficient to cause large scale melting of arctic sea ice and the Greenland ice sheet. Such a change in the current may be gradual (over centuries) or very rapid (over a few years).
Presents high-quality research on deep ocean basins and the global mid-ocean ridge system Marine Geophysical Research (MGR) has a long-established reputation for high quality geophysical research and data on deep ocean basins. Reflecting international efforts to better understand the global mid-ocean ridge system, its focus has broadened to include studies of continental margin geophysics, structure, stratigraphy and sediment deposition processes. The editors of MGR anticipate a rising rate of advances in this sphere in coming years, reflecting the diversity and complexity of processes in the margins. The range of coverage of Marine Geophysical Research extends to: new techniques for imaging the deep sea floor the development of new tools for measuring the physical properties of sediments and rocks in continental and oceanic plate margins, as well as ridge settings.
Meteor Strike A meteor burst into a fireball over Siberia. Can we spot the next deadly asteroid in time? 52:53 Air Date 03/27/13 Mind of a Rampage Killer Can science help us understand why some people commit horrific acts of mass murder?
Earth New Report: Responding to the Challenge of Climate and Environmental Change NASA's Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space Earth is a complex, dynamic system we do not yet fully understand. The Earth system, like the human body, comprises diverse components that interact in complex ways. We need to understand the Earth's atmosphere, lithosphere, hydrosphere, cryosphere, and biosphere as a single connected system.
The Plate Tectonic Globe™ The Plate Tectonic Globe™ is a globe unlike any other currently on the market. Its unique hand-crafted design illustrates clearly and accurately Earth's crustal tectonic features in vivid relief.
The Breakup of Pangea (drag mouse over map to animate) http://www.scotese.com/pangeanim.htm E Continental Divide: Interactive Animation http://www.exploratorium.edu/origins/antarctica/ideas/gondwana2.html Earth's Continental Plates http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml