Sunday's megaquake was not the first time, or even the second, that a major geological event in Indonesia has killed tens of thousands.

From the 1815 eruption of Mt. Tambora to the 1883 explosion of Krakatoa, Indonesia's seismic tragedies of the past two centuries have altered human history well beyond the Pacific's so-called Ring of Fire, sending geopolitical, economic, and even artistic repercussions across the planet.

The havoc wrought by the tsunami that swamped southern Asia Sunday is a stark reminder that humanity is bound together as much by geological forces - often unseen and occasionally devastating - as by the tides of commerce and culture.

This latest natural disaster will have profound effects on the politics and economies of the Indian Ocean. Separatist movements in Sri Lanka and in Indonesia's Aceh province suffered thousands of casualties, and India's pummeled Nicobar and Andaman islands have often been used by rebels from both movements.

How well governments respond to the tragedy, say historians, could shape those conflicts and their nations for years to come. "Some people think natural calamities are a signal from god," says Taufik Abdullah, an Indonesian historian trained at Cornell University. Historically "quite often natural rebellions have triggered social rebellions," he says.

Indonesian quakes have touched off global political aftershocks before.

The 1883 eruption of Krakatoa off southern Sumatra is considered by some historians to be the world's first global media event. The invention of the telegraph and creation of news services like Reuters allowed Americans "to read of the devastation over breakfast the next day," says Simon Winchester, a trained geologist and author of the 2003 book "Krakatoa: The Day the World Exploded."

Tsunamis generated by that eruption killed 40,000 on Java and Sumatra. The explosion was heard as far away as Australia and India, and threw millions of tons of ash into the atmosphere that affected global weather for years. Krakatoa's ash helped cool temperatures around the world and led to stunning sunsets in Europe and the US that captivated artists.

Late Hudson River School painters were drawn to the gaudy evening skies, and some art historians now believe the blood-red heavens in Edvard Munch's iconic painting of alienation and fear, "The Scream," were inspired by those sunsets.

In Europe, Mary Shelley penned her grim tale of Frankenstein while huddled inside that year, and her literary friend Lord Byron wrote, "the bright sun was extinguish'd..., and the icy earth swung blind and blackening in the moonless air."

The 1883 explosion also helped generate one of the largest early challenges to Dutch colonial rule in the archipelago, and also planted the first seeds of modern Islamist political activity in Indonesia.

Imams on the northwest coast of Java preached that the eruption was a sign of Allah's displeasure at infidel rule, and urged a violent jihad, according to Sartono Kartodirdjo, am Indonesian historian.

The Dutch knew the political stakes, and knew that improved global communications would bring unprecedented scrutiny to the disaster, says Mr. Winchester, by phone from his home in England.

"The Dutch made this superhuman effort to bring relief to the area because they were aware of the significance of the event and that the Muslim clerics were quickly making political capital from the event," he says.

Nevertheless, emboldened clerics and destitute peasant communities sharpened their rhetoric and began an assassination campaign against Dutch officials and planters, culminating in the Banten peasants' revolt of 1888 that killed dozens of Dutch and hundreds of Indonesians.

That failed movement helped further the cause of Indonesian nationalism and eventual independence, as well as the country's minor strain of Islamist movements that find their modern expression in the Jemaah Islamiyah terrorist group that killed over 200 in an attack on a Bali nightclub in 2002.

The 1815 eruption of Mt. Tambora, too, had far-reaching effects. It killed 100,000 people on Sumbawa island and spewed so much ash into the air that 1816 became known in the US and England as "the year without a summer."

Some historians say that crop failures in New England that year spurred an exodus of tens of thousands of farmers to more-fertile soils of the Midwest, speeding the American conquest of the continent....