For decades, scientists have known that activities like mining, drilling and building dams can actually create earthquakes. As early as the 1960s, observers noted that deep-earth gold mining changed the stresses in rocks and caused earthquakes. Above, miners drill into the rock at the Sub Nigel East Gold Mine in Johannesburg in 1961, more than 6,000 feet below ground.
Small earthquakes in Ohio and Arkansas associated with hydraulic fracturing for gas have taken many people by surprise. Gas industry executives say there's no hard evidence that their activities are causing these quakes. But some scientists say it's certainly possible; in fact, people have been causing quakes for years.
In the 1960s, geologists realized that gold mines in South Africa had created small earthquakes. Caverns dug into the earth thousands of feet below the surface collapsed. The "pancake" effect caused quakes, in one case a magnitude 5.2 temblor.
For two decades, the Pentagon has maintained that it could fight two wars at the same time. But as the Obama administration releases its new military strategy Thursday, some question whether the Pentagon will abandon that long-held commitment.
An early draft of the Pentagon's new strategy, The New York Times reported, said the military would only be able to win one war and spoil an adversary's efforts in a second war.
Renewable energy is growing rapidly in the U.S., with wind and solar industries enjoying double-digit growth each year. Part of that growth comes from more homeowners choosing to install solar panels.
With government subsidies, some people can even make a financial argument for installing the panels. But in recent years, the price of one fossil fuel — natural gas — has declined so much that solar panels are having difficulty competing.