A volcano on the Italian island of Stromboli exploded on November 16, Live Science reported. The eruption, which was caught on tape, sent ash flying hundreds of feet into the air. Volcanoes often arise from tectonic plate motions.
According to Live Science, a sudden eruption recently rocked a small Italian island. “An explosion on the slopes of Stromboli sent an avalanche of pyroclastic flow rushing down the side of the Italian volcano,” the article said. “The stronger-than-usual explosion was captured on cameras operated by the Istituto Nazionale Geofisica e Vulcanologia.
“Video captured by infrared cameras shows the ultra-hot initial eruption and the slightly cooler cloud of ash and gases careening downslope. This avalanche of hot ash and gases is known as pyroclastic flow.”
Volcanoes are often created by dynamic geological events involving the motions of tectonic plates.
Tectonic plates have boundaries, just like the edges of pieces in a slider puzzle. Those boundaries can converge, meaning they push against each other; they can diverge, or move apart; or they can transform, which in this context means scrape alongside each other. Divergent boundaries are the key to volcanoes.
“Divergent boundaries always mark elongated zones along which new crust is formed; formed as volcanic material,” said Dr. Robert M. Hazen, Clarence J. Robinson Professor of Earth Sciences at George Mason University in Fairfax, VA. “Two plates are going to diverge above a region where a mantle convection brings heat to the surface.”
The Earth’s mantle, under its crust, often transfers heat from the Earth’s core up to the surface. The process of the mantle moving as it does so is known as mantle convection. Divergent boundaries occur where volcanic material moves upward.
“That excess heat causes partial melting of the near-surface rocks; this supplies magma to these volcanoes, as the plates move apart,” Dr. Hazen said. “The lava produced at ridges is typically a basalt: that’s a dense, black rock, rich in silicon and oxygen, magnesium and iron, just like the mantle. Basalt forms the foundation for all of the ocean crust in the Earth.”
Dr. Hazen said that the most famous divergent boundary is the Mid-Atlantic Ridge, which was discovered in the 1950s and extends for 60,000 kilometers. It’s also spreading at a rate of two to four centimeters—about an inch—every year.
“You can actually make satellite measurements, laser measurements that can detect that increasing distance,” he said. “This is how it works: You have two points that are set in rock; one in North America, one in Europe. You have laser satellites that can measure distances to better than a fraction of an inch; and, therefore, you can measure the distance between North America and Europe, and year by year that distance is getting longer.”
This amazing technology has helped support theories about how long it took the Atlantic Ocean to “open up.” Dr. Hazen said that the Atlantic is roughly 3,000 miles across, and, of course, each mile is 5,280 feet, so the ocean is roughly 15,840,000 feet across. Each foot is 12 inches, which makes the Atlantic Ocean about 190 million inches wide.
If the Atlantic Ocean is diverging at an inch per year, it took 190 million years to get where we are today. As long as that may seem, it’s a short period compared to the Earth’s overall age.
Dr. Robert M. Hazen contributed to this article. Dr. Hazen is Clarence J. Robinson Professor of Earth Sciences at George Mason University in Fairfax, VA, and a research scientist at the Geophysical Laboratory of the Carnegie Institution of Washington. Dr. Hazen earned his bachelor’s and master’s degrees in geology from the Massachusetts Institute of Technology. He earned a PhD in Earth Science from Harvard University.