What caused a temporary but dramatic change in climate in 1816 called the Year without a Summer?

On April 10, 1815, Mount Tambora erupted on the Indonesian island of Sumbawa after what some scientists believe was a period of inactivity of about 5,000 years. The

The scenic geysers and hot springs of Yellowstone are the result of volcanic activity just under the surface of the famous national park.

The scenic geysers and hot springs of Yellowstone are the result of volcanic activity just under the surface of the famous national park.

Is Yellowstone actually a supervolcano?

Yellowstone National Park is renowned for its scenic geysers and hot springs covering some 2,300 square miles (3,800 square kilometers). The energy for all this hot water actually comes from volcanic energy below a plateau that is actually a giant caldera. Geologists estimate that this massive volcano last erupted about 640,000 years ago with an energy equal to 8,000 Mount St. Helens eruptions. One can only imagine the destruction such an explosion would have wreaked. A nuclear winter would have ensued, acid rain would have fallen from the sky, and some scientists believe that the human race was driven almost to extinction at the time.

Since the volcano is still active, it could happen again at almost any time. Some parts of Yellowstone have risen about 29 inches (74 centimeters) since measurements were first taken in 1923, which indicates a buildup of magma beneath the crust. It is only a matter of time before this energy is released. And Yellowstone is not the only such supervolcano. The last such eruption came from Toba, Sumatra, about 70,000 to 75,000 years ago, and other, as-yet-undiscovered supervolcanoes might exist.

massive blast shot an estimated 24 cubic miles (100 cubic kilometers) of rock and 220 million tons (199.54 billion kilograms) of sulfur dioxide almost 29 miles (40 kilometers) into the atmosphere. Everything within 400 miles (645 kilometers) of the blast was plunged into near total darkness. Tsunamis reaching 16 feet (five meters) in height crashed onto surrounding shorelines. After the initial eruption, the volcano continued to erupt through mid July.

To make matters worse, two previous volcanic eruptions also contributed to dust and debris being thrown into the Earth's atmosphere. The volcano Soufrière St. Vincent erupted in the Caribbean in 1812, and two years later Mayon Volcano exploded in the Philippines. In addition to all this volcanic activity, there was an increase in sunspot activity, including one particularly large sunspot that was so big it could be seen with the naked eye.

All of these events conspired to lower temperatures dramatically all over the planet. Canada, Europe, and the United States were all very hard hit, particularly in the East and Midwest, where crop failures were extensive in 1816. During that summer, snow fell a few times in New England in June. Vermont saw ice on its lakes in June thick enough to skate on, while snow was as deep as 18 to 20 inches (45 to 50 centimeters) deep. After this bizarrely cold summer, the winter of 1816 to 1817 was rather mild, but that did not matter since the crops were all ruined.

What happened when Mt. St. Helens erupted?

On the morning of May 18, 1980, a magnitude 5.1 earthquake struck beneath the Mt. St. Helens volcano in Washington state. Later that day, the volcano exploded, initiating a massive avalanche that tore away the northern slope of the mountain and created the largest landslide in recorded history. The conical volcano went from about 9,678 feet (2,950 meters) to 8,366 feet (2,550 meters) in height, releasing a giant plume of ash and gas high into the atmosphere. A lethal pyroclastic flow of hot steam, gas, and rock debris raced down the slope of the mountain, traveling as fast as 684 miles (1,100 kilometers) per hour.

A fine ash dust was propelled into the upper atmosphere (stratosphere) at heights reaching up to 15 miles (22 kilometers), spreading to the east by the prevailing westerly winds and eventually reaching all over the world. In a short time, the ash blanketed central Washington, the prevailing winds carrying an estimated 540 million tons of ash across 22,007 square miles (57,000 square kilometers) of the western United States. People in towns nearby (and some as far away as western Montana) were affected by the rain of ash. Car radiators were clogged, upper respiratory problems worsened, air and ground travel were disrupted, and a thick coating of ash particles covered everything outside. Despite such impressive statistics, the Mt. St. Helens eruption did not disrupt climate on a worldwide scale. There are two reasons for this: 1) the volcano did not release that much sulfur dioxide compared to some other major eruptions, and 2) the eruption blew out the side of the mountain, thus shooting debris at an angle and not as high into the atmosphere as might have otherwise happened.

What two volcanic eruptions had the biggest impacts on the climate in the twentieth century?

The eruption of El Chichón in southern Mexico, which lasted from March 29 through April 4, 1982, and the June 15, 1991, eruption of Mt. Pinatubo in the Philippines caused significant disruptions to the planet's climate. El Chichón shot about 7.75 million tons (over 7 billion kilograms) of sulfur dioxide into the atmosphere, as well as some 24.25 million tons (22 billion kilograms) of other dust and particles. Coincidentally, there was a strong El Niño building at the same time. While the El Niño effect worked to warm ocean waters, the El Chichón eruption was cooling the atmosphere, and the result was that the two effectively cancelled each other out. That summer, when temperatures should have increased because of El Niño, the

Smoke emerges from Mt. St. Helens before its 1980 eruption.

Smoke emerges from Mt. St. Helens before its 1980 eruption.

average temperatures were actually fairly normal. During the winter of 1982 to 1983, though, temperatures in Europe, Siberia, and North America were higher than normal, and temperatures in the Middle East, China, Greenland, and Alaska were cooler. This was because the gases from El Chichón had caused an arctic oscillation in the stratosphere, changing air current patterns.

When Mount Pinatubo erupted, it sent 20 million tons of sulfur dioxide into the sky, and estimates are that this resulted in an average worldwide temperature drop of 1.7°F (0.8°C) in 1992. The effects continued through 1993, as the haze produced by the extra sulfur dioxide in the atmosphere reflected the Sun's rays.

What is the Ring of Fire?

There is a circular region that surrounds the Pacific Ocean where volcanic activity is particularly high. This is known as the "Ring of Fire" and includes coastal areas in Japan, Russia, Alaska, Canada, Oregon, Washington state, California, Mexico, Southeast Asia, and many South Pacific islands. The ring stretches some 40,000 miles (64,000 kilometers) and includes three-fourths of the planet's volcanoes. Among those are Mt. St. Helens and recently active volcanoes in Alaska, such as Mount Spur, which erupted in 1992, and Mt. Redoubt, which erupted March 22, 2009, near Anchorage.

< Prev   CONTENTS   Next >