From EARTH Magazine  --  You have probably heard of “100-year floods” and “500-year droughts,” and perhaps you’ve seen signposts near rivers showing when the last big flood was or statements about when the last severe drought occurred. But do you really know what those terms mean, or what your likelihood is of experiencing such a hazard in any given year? Probably not, according to Richard Vogel of Tufts University, because although such terms have long helped policymakers and the public try to make sense of severe weather, they may confuse the issue more than clarify it.

From EARTH Magazine  --  Afghanistan is one of the world's poorest countries, with an economy largely based on subsistence agriculture. Working in an arid climate on thin margins of profitability and sustenance, Afghan farmers depend on reliable, year-round sources of surface water and groundwater to irrigate their crops and water their livestock. Seasonal flows of streams and rivers fed by melting snowpack high in Afghanistan's mountains also recharge alluvial aquifers located in populated valleys and provide city dwellers with drinking water. But the arid

From EARTH Magazine  --  The vaguely familiar, yet primeval landscape of New Zealand served as the backdrop for the blockbuster film adaptations of the entire "The Lord of the Rings" trilogy and "The Hobbit" trilogy, the third and final installment of which opens widely this week. The geology that created this landscape is front and center in EARTH's February cover story, "The Geology of Middle-earth."

From EARTH Magazine  --  Methane is often found naturally leaking from the seafloor, particularly in petroleum basins like the Gulf of Mexico or along tectonically active continental margins like the U.S. West Coast, but such plumes were not expected along passive margins, like the East Coast of North America. Now, however, the discovery of hundreds of methane seeps on the seafloor along the U.S. East Coast suggests that such reservoirs may be more common along passive margins than previously thought.

From EARTH Magazine  --  Hurricane Sandy struck the U.S. East Coast in October 2012, leaving about $65 billion of damage in its wake and raising the question of how to mitigate the damage from future storms. It's a question that arises in the wake of most natural disasters: What steps can society take to protect itself from storms, floods, landslides, earthquakes, tsunamis or volcanic eruptions? But the question itself illustrates the complexity of preparing for natural disasters.

From EARTH Magazine  --  On March 13, 1989, a geomagnetic storm spawned by a solar outburst struck Earth, triggering instabilities in the electric-power grid that serves much of eastern Canada and the U.S. The storm led to blackouts for more than 6 million customers and caused tens of millions of dollars in damages and economic losses. More than 25 years later, the possibility of another such catastrophe still looms, and the day-to-day effects of space weather on electrical systems remain difficult to quantify.

From Earth Magazine  --  Earth's abundant silicate minerals are degraded over time by exposure to water, chemical dissolution, and physical and chemical weathering by tree roots and even insects such as ants and termites. Such weathering plays a significant role in decreasing carbon dioxide in the atmosphere, as carbon dioxide is consumed in chemical weathering reactions and the resultant carbonate becomes sequestered in the form of limestone and dolomite.

From EARTH Magazine  --  When large earthquakes hit Earth in quick succession, many people wonder if the events are linked. Scientists generally say that such events aren't linked, but the latest research seems to indicate that a large earthquake can potentially trigger another quake hundreds or even thousands of kilometers away in a process called dynamic triggering. However, when it could happen is far from predictable.

Hawaii's Kilauea volcano is famously effusive: Low-viscosity lava has been oozing out of the main caldera and two active rift zones along the southern shore of the Big Island since 1983. But scientists suspect that Kilauea's eruptions haven't always been so mild. In the past 2,500 years, at least two cycles of explosive eruptions lasting several centuries each have rocked the island. The switch from effusive to explosive is likely to occur again, scientists say, but probably not anytime soon.

From EARTH Magazine  --  When Francisco Pizarro landed in Peru in 1532, his band of Spanish conquistadors set off a chain of far-reaching consequences for the people and economics of western South America. The Chira Beach-Ridge Plain in northwestern Peru is rippled by a set of nine ridges — several meters tall by up to 300 meters wide and 40 kilometers long, and large enough to be visible from space — running parallel to the shoreline. The pattern, observed along at least five other Peruvian beaches, was thought to have formed naturally over the past 5,000 years.