A Visit to Alaska’s Volcanic Islands and a ‘Journey to the Center of the Earth’
by Carolyn Sotka
Augustine Volcano Viewed from the M/V Maritime Maid. Photo courtesy Cyrus Read and AVO
Pavlof volcano steaming, as viewed from Nelson Lagoon. December 5, 2014. Photo courtesy of Merle Brandell and AVO
When one hears the term ‘signs of significant unrest’ we typically think of geo-political uprisings or other demonstrations against social injustice. But in Alaska, the term is used to describe the activity (or inactivity) of over 130 volcanoes and volcanic fields. Approximately 50 of these have been active within historical time (since about 1760, for Alaska) and make up more than three-quarters of United States volcanoes that have erupted in the last two hundred years.
Pavlof volcano, earthshadow, and almost-full moon, December 4, 2014. Photo courtesy of Royce Snapp and AVO
There are currently two active volcanoes, Pavlof and Cleveland, that are closely monitored by the Alaska Volcano Observatory, a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks and the Alaska Division of Geological and Geophysical Surveys. These and other volcanoes along the Aleutian Island chain create a beautiful backdrop for stunning imagery taken from land and from space.
Map of Alaska’s volcanoes along the Aleutian Trench. Interactive map available at AVO.
Cleveland last erupted in 2006 and in a fortuitous opportunity, was captured by astronauts at the International Space Station. Photo from NASA.
Cleveland is one of four volcanoes that make up the Islands of the Four Mountains in the Aleutian archipelago of Alaska. Landsat 8, an American earth observation satellite launched in early 2014, took these satellite images of the volcanoes in winter and in summer.
Herbert (lower left), Cleveland (center), Carlisle (upper left), and Tana (the rugged one to the right). The lower flanks of the volcanoes are relatively clear, but clouds form higher up; as the wind blows up the windward face of the mountains it cools, and clouds form as water condenses out. Photos by NASA Earth Observatory/Jesse Allen, using Landsat data from the U.S. Geological Survey.
Perhaps best described by Slate’s ‘Bad Astronomy’ blogger Phil Plait – these images evoke a sense that our planet ‘is not done cooking.’ Indeed, it’s slightly terrifying to think that all that separates us from the ‘vast ball of superheated rock and iron’ is a thin veneer of rock.
Volcanoes are formed at the boundaries of continental plates when vents open and magna, ash and gasses are released from the mantle. Earth’s crust is broken into 17 major, rigid tectonic plates that float atop the mantle. Magma is called molten rock when in the mantle and lava after released to the earth’s surface.
The volcanoes of the Alaskan islands are part of the ‘Ring of Fire’ region in the Pacific basin. The Ring of Fire forms a continuous series of oceanic trenches, volcanic arcs and belts and plate movements.
The u-shaped Ring of Fire is where 90% of the world’s earthquakes happen and 80% of largest earthquakes occur.
Moving beyond the crust, mantle and outer core – the inner core is actually a solid unlike the movie “Journey to the Center of the Earth’ (twice adapted from Jules Verne’s novel), and NOTHING is alive there, although it may have been liquid 2-4 billion years ago. The furthest humans have ‘journeyed to the center of the earth’ is about 12 km down which is a third of the way thru the crust and over 5000 km away from the inner core.
Within the inner core, pressure is over 3 million atmospheres and temperatures can rise to over 10,000 degrees Fahrenheit. It’s this extreme pressure that “freezes” the inner core into a solid. This inner core rotates at 0.3 to 0.5 degrees per year more than the Earth’s surface and likely acts to stabilize the magnetic field created by the outer core.
We owe our existence to this spinning sphere of heated metal that generated the tectonic forces to create earth’s landmasses, and the continental drift that has forced life on earth to evolve.
Check out the BBC special, ‘Ten Things you Didn’t Know about Volcanoes’ to learn about the ancient myths about the creation of volcanoes a host of other interesting facts and tidbits. – CS