How Volcanoes Shape the Earth
Without the heat and nutrients provided by the earliest volcanic eruptions, life may never have originated on Earth. But the same volcanoes that helped spark life also can be very destructive.
Throughout history, they have wiped out entire civilizations — and the next earth-shattering eruption could happen anytime.
Did electricity spark life on Earth?
A few million years after Earth’s formation, its surface was dominated by volcanoes, most of which were submarine. This environment, while extremely hostile, provided the basis for the gradual development of plants, animals and humans.
Although the sun was much weaker then than it is today, volcanoes spewed large amounts of greenhouse gases into the atmosphere, enabling the planet to trap the limited heat from the sun.
Volcanoes also outgassed water vapor, which helped make the oceans; these contained amino acids that may have been delivered by meteors or been created during meteor strikes. In the warm primordial water, rich with volcanic sulfur particles, more and more amino acids were generated, but this alone did not create life.
One theory holds that lightning striking the ocean caused the amino acids to combine into proteins, the foundation of cells. Life on Earth may have begun in a soup of water, sulfur and lightning.
Dinosaurs are the most famous prehistoric animals, but they weren’t the first. They were preceded by big creatures, including Crurotarsi, that were wiped out by volcanic supereruptions 200 million years ago. The dinosaurs that had been living in their shadow for 30 million years thus began to thrive when the Crurotarsi became extinct. Dinosaurs assumed dominance and thrived for the next 135 million years — until they went extinct too.
Massive ash cloud cooled the planet
During the 4.5 billion years of Earth’s existence, people have been in the picture only for a short time. And our story could have ended before it even began.
A huge volcanic eruption in Sumatra, Indonesia, came very close to wiping out the ancestors of humans between 69,000 and 77,000 years ago. The Toba volcano erupted with such force that its caldera covered 1,158 square miles. It spewed out 2,800 billion cubic meters of magma, 800 billion of which were ash. This ash settled in a layer about 6 inches thick that blanketed southern Asia — and, worse, became trapped in the atmosphere, blocking out the sun. The resulting volcanic winter lasted six to 10 years and ushered in a cool period for the next millennium.
The massive eruption had a dramatic and negative impact on all life, including people. One theory holds that the world’s entire human population was reduced to somewhere between 10,000 and 15,000 individuals.
Throughout Earth’s history, several extinction events have taken place. The largest one happened about 250 million years ago and is called the Great Dying.
Scientists theorize that a single devastating event killed off most life-forms on Earth. It could have been a series of large asteroid strikes, a massive emission from the seafloor of the greenhouse gas methane, or increased volcanic activity, such as the eruptions that created the Siberian Traps that now cover some 770,000 square miles of Russia. When the mass extinction ended, 57 percent of all animal families and 83 percent of all genera had disappeared from the planet, and it took some 10 million years for life to recover.
Civilizations thrive on the ashes
One of history’s most successful civilizations was the Maya, which ruled Central America from around 800 BCE to 1530. Many Maya settlements were situated in mountainous regions on or near towering volcanoes that were blanketed with the nutrient-rich soil. This supported the agricultural foundation that helped the Maya to flourish. The volcanoes also had large deposits of obsidian, a glassy black volcanic rock used to make swords and religious figurines.
Many other civilizations — the Etruscans in northern Italy, the ancient civilizations of Greece, the Roman Empire — have also benefited from living in proximity to volcanoes. The same thing occurred in several places in Asia, where various cultures took root near volcanoes.
The secret behind the rich, agriculture-friendly soil found on volcanic slopes Is that it’s loaded with nutrients and minerals brought to the surface from deep under the ground during eruptions. Earth’s modern surface largely results from the millions of volcanoes that spewed huge amounts of magma and volcanic ash on the young planet. Lava and ash contain huge amounts of sulfur and nitrogen, which can be used to fertilize crops.
Lava contains gold, silver and gemstones
Lava is rife with precious metals and minerals, particularly gold, silver and diamonds — relatively rare materials that have long held great value for people in many different civilizations.
Volcanic eruptions throughout the world have resulted in deposits of a variety of valuable raw materials. Diamonds reach the surface via a rare type of magma, kimberlite, which is typically found 125 miles underground. But the richest deposits are found in magma that has not yet reached Earth’s surface, but that has hardened in great massifs that lie beneath the volcano itself.
Pompeii was destroyed by a river of hot volcanic ash
On Aug. 24,79, the residents of the Roman city of Pompeii woke up to a day that seemed like any other. A celebration honoring Vulcan, the god of fire and volcanoes, had been held the day before, but to no avail. Before the night was over. Mount Vesuvius had exploded, spewing out a cloud of volcanic material that reached some 30 miles in height — more than 1 million tons of red-hot rock and lava per second. All life was wiped out within six miles of the mountain, due in large part to the superhot pyroclastic flow of gas, ash and rock that surged across the area in a matter of moments, killing thousands of people nearly instantly. Up to 80 feet of ash fell in only six hours; it hardened, encapsulating and preserving the city, which was not rediscovered until 1738.
3.6″F drop in the average global temperature
Although no eyewitness accounts exist, analyses of ash layers and the size of the caldera as compared to that left by the eruption of Krakatoa in Indonesia in 1883 have provided geologists with a good idea of the extent of the Thera event. Krakatoa killed more than 36,000 people in just a few hours, generated 39-foot tsunamis, spread ash across all of Asia and lowered the average global temperature 1 degree. The Thera eruption was four to five times as violent and caused the average temperature of the planet of all by more than 3 degrees.
Fertile land emerges from the ruins
In 1963, the story of the formation of new land spread across the world. In the ocean off Reykjavik, Iceland, fishermen had discovered that lava from an erupting volcano had formed a small island, which was named Surtsey. And it’s not alone. In recent years, emerging volcanic land has been found in several places.
The Canary Islands are gaining a sister off the island of El Hierro, and in the Red Sea a new island sprang up in the Zubair group after an eruption in 2011, joining the other small islands in the group that were formed in the same way. Off Tonga, a pinpoint island called Home Reef was created in 2006 by a volcano that previously erupted in 1852,1857 and 1984; volcanologists expect the islet to keep growing.
All of the Hawaiian islands were made by volcanoes, and a new one may eventually join them. It’s now 3,000 feet from the surface, and scientists think that it will break the waves in 50,000 years.
86% of Iceland is heated by the Earth
Icelanders have developed a symbiotic relationship with the magma that lies below their volcano-studded country, using it to heat a network of water-filled pipes that provide heat to 86 percent of Icelanders’ homes. Although it has proved difficult to fully utilize the island’s geothermal energy, new technology is opening up new opportunities. In 2020, Iceland will begin supplying the United Kingdom with energy via a 930-mile submarine cable, and scientists hope one day to establish volcanic power plants, in which artificially maintained eruptions produce energy.
A supervolcano could change life as we know it
The force of a supervolcano is so great that one of them may ultimately doom humankind. They’ve already wiped out a large number of animal species and have come much too close to exterminating us on more than one occasion.
Many scientists think that humans could potentially survive a supervolcano erupting — but it wouldn’t be easy, especially if it were one of the six land-based supervolcanoes. The first victims would be those living closest to the volcano, but unlike a smaller eruption, the kill zone would cover a large area: If Yellowstone blows, everyone in all of the states surrounding Wyoming could be at risk of dying. Volcanologists estimate that a layer of ash 3 feet deep would settle across fully half the United States, with smaller amounts covering the rest of the country.
The supervolcano would spew such massive amounts of ash into the atmosphere that most sunlight would be blocked out, lowering the average global temperature by more than 5 degrees, devastating agriculture worldwide and triggering a prolonged period of famine.