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WASHINGTON — Tornadoes, hurricanes, blizzards, floods, wildfires, earthquakes, tsunamis: Mother Nature seems to have it in for our world these days.

In a way, though, we live in a relatively peaceful time. While it's no comfort to those hurting or grieving now, Earth saw far greater catastrophes in its long and troubled past.

The planet has been frozen, roasted, smothered, battered, shaken, half-drowned. Entire species have been obliterated; so far, fortunately, that doesn't include Homo sapiens, but we've had a close call.

And these are all natural calamities, not those caused by humans, such as war, terrorism or the Holocaust.

"The history of life may have been shaped by major catastrophes to a far greater extent than previously realized," Trevor Palmer, a biologist at Britain's Nottingham Trent University, wrote in his 2003 book, "Perilous Planet Earth."

Researchers have collected evidence of at least five major extinctions, dated at 65, 200, 250, 360 and 440 million years ago.

In the most recent episode, an asteroid 6 miles across slammed into what is now an area off the Yucatan Peninsula, killing off the dinosaurs and many other creatures.

The biggest extinction of all, 250 million years ago, is known as "The Great Dying" because more than 80 percent of the species then alive disappeared.

This was a "far greater crisis than the extinction of dinosaurs 65 million years ago," said Douglas Erwin, a paleobiologist at the National Museum of Natural History in Washington.

"Plants and animals came closer to complete elimination than at any point since they first evolved," he wrote in his 2006 book, "Extinction."

Earth's calamities included collisions with asteroids and comets, eruptions of supervolcanoes, massive lava flows engulfing millions of square miles, shattering earthquakes and devastating tsunamis.

A huge volcanic explosion 75,000 years ago at Mount Toba, in what is now Indonesia, blasted an estimated 700 cubic miles of ash and dust into the atmosphere, shrouding the entire Earth.

The Toba eruption coincided with the beginning of the latest ice age and may have almost wiped out our ancestors. DNA evidence shows the human population shrank to about 10,000 at that time, according to Jelle de Boer, an Earth scientist at Wesleyan University in Middletown, Conn.

Most catastrophes aren't bad enough to cause an extinction, but they create tremendous havoc. Sometimes they've contributed to the rise and fall of civilizations.

A rash of climate disasters about 2,300 years ago may have led to multiple civilization collapses in Egypt, the Middle East, India and China, according to Benny Peiser, an anthropologist at Liverpool John Moores University in England.

Peiser speculated that the troubles may have been caused by the breakup of a comet in the atmosphere, like the one that hit Jupiter in July 1994.

Ninety-nine years ago, a 50-yard-wide meteoroid exploded in the air over a remote area of Siberia, leveling 830 square miles of forest.

An earthquake in China in 1556 killed 800,000 people. Another 60,000 perished in Lisbon, Portugal, in 1775. Tokyo and Yokohama lost 200,000 in 1923.

In 1815, a massive eruption of the volcano Tambora in Indonesia blocked the sun for two days, leading to a "year without summer" in Europe and North America.

Another Indonesian volcano, Krakatoa, left 40,000 dead after an eruption in 1883.

About 250 million years ago, at least 240,000 cubic miles — yes, miles — of lava gushed from a subterranean chamber below Siberia, blanketing an area the size of Europe and polluting the atmosphere with poisonous fumes.

The world has experienced repeated episodes of global warming due to natural, not human, causes: variations in the sun's radiance, wobbles in the Earth's orbit, massive emissions of carbon dioxide and other greenhouse gases.

These hot spells have alternated with lengthy ice ages that uprooted plants and animals and drove many to extinction.

On at least one occasion, about 600 million years ago, the Earth was nearly covered in snow and ice, with only the tips of a few volcanoes poking through. Greenhouse gases from the volcanoes eventually warmed the planet enough to melt the snow and let life flourish anew.

On StarNet: Find several multimedia features about earthquakes, tsunamis and volcanos at azstarnet.com/science