They happened at the same time, halfway around the globe from each other. They both shook the world.

On March 11, 2011, at 2:46 in the afternoon Japan time, 17 miles below the seabed, the pressure vast tectonic between two plate created a massive violent upward force that set off one of the most powerful earthquakes ever recorded. In addition to widespread damage to buildings and infrastructure in the region north of Tokyo, the quake also knocked out the power supply, including that to the Fukushima Daiichi nuclear complex. Fifty- five minutes later, a huge tsunami unleashed by the quake swept over the coast, drowning thousands and thousands of people. At the Fukushima Daiichi complex, located at the very edge of the ocean, the massive tsunami surged above the seawall and flooded the power station, including its backup diesel generator, depriving the hot nuclear reactors of the cooling water required to keep them under control. In the days that followed, explosions damaged the plants, radiation was released, and severe meltdowns of nuclear rods occurred.

The result was the worst nuclear accident since the explosion at the Chernobyl nuclear plant in Soviet Ukraine a quarter century earlier. The Fukushima accident, compounded by damage to other electric generating plants in the area, led to power shortages, forcing rolling blackouts that demonstrated the vulnerability of modern society to a sudden shortage of energy supply. The effects were not limited to one country. The loss of industrial production in Japan disrupted global supply chains, halting automobile and electronics production in North America and Europe, and hitting the global economy. The accident at Fukushima threw a great question mark over the "global nuclear renaissance," which many had thought essential to help meet the power needs of a growing world economy.

On the other side of the world, a very different kind of crisis was unfolding. It had been triggered a few months earlier not by the clash of tectonic plates, but by a young fruit seller in the Tunisian town of Sidi Bouzid. Frustrated by constant harassment by the town's police and by the indifference of local officials, he doused himself with paint thinner and set himself aflame in protest in front of the city hall. His story and the ensuing demonstrations, transmitted by mobile phones, Internet, and satellite, whipped across Tunisia, the rest of North Africa, and the Middle East. In the face of swelling protests, the regime in Tunisia collapsed. And then, as protesters filled Tahrir Square in Cairo, so did the government in Egypt. Demonstrations against authoritarian governments spread across the entire region. In Libya, the protests turned into a civilwar in which drew in NATO.

The global oil price shot up in response not only to the loss of petroleum exports from Libya, but also to the disruption of the geostrategic balance that had underpinned the Middle East for decades. Anxiety mounted as to what the unrest might mean for the Persian Gulf, which supplies 40 percent of the oil sold into world markets, and for its customers around the globe.

These two very different but concurrent sets of events, oceans away from each other, delivered shocks to global markets. The renewed uncertainty and insecurity about energy, and the anticipation of deeper crisis, underscored a fundamental reality – how important energy is to the world.

From The Quest: Energy, Security, and the Remaking of the Modern World by Daniel Yergin. Reprinted by arrangement of Penguin Press, a member of Penguin Group (USA), Inc. Copyright 2011 by Daniel Yergin.