University of Alberta
A sample of ancient rock from the Acasta Gneiss Complex in the Northwest Territories.
NASA has opened voting for itsTournamentEarth 2014 photo competition
, which takes Earth images captured by satellite and makes them go head to head. Users (that's you!) vote on the best shots, which then go on to the final round. You can create your interactive brackethere
. Note: Voting ends Friday, March 14. Our favorite to take the whole thing: An eruption at Kliuchevskoi, a stratovolcano on the Kamchatka Peninsula of Russia (above) was photographed by the Expedition 38 crew aboard the International Space Station.PHOTOS: 2013 Top 20 Earth Images Contest
NASA/ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Center
Tristan da Cunha, an island in the southern Atlantic Ocean, is more than 2,300 miles (3,700 kilometers) from the coastline of Antarctica. A volcano sits at the island's center. "The last known eruption of Tristan da Cunha took place in 1961–1962," writes William L. Stefanov for NASA, "and forced the evacuation of the only settlement on the island, Edinburgh of the Seven Seas, on the northern coastline (obscured by clouds in this image). The town is considered to be the most remote permanent settlement on Earth, with its nearest neighbor located 2,173 kilometers (1,347 miles) to the northeast on the island of St. Helena."PHOTOS: Changing Face of Earth in 2013
NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response Team at NASA GSFC.
Alaska is the cloudiest region of the United States, reports the space agency, but last summer, NASA's Terra satellite caught a rare, nearly cloud-free view.PHOTOS: The Stinkiest Places on Earth
NASA Earth Observatory images by Holli Riebeek, using Landsat 8 data from the USGS Earth Explorer
In early November of 2013, a large iceberg calved off the front of Antarctica’s Pine Island Glacier, which was captured by the Operational Land Imager on the Landsat 8 satellite.PHOTOS: A View of the Unnatural World From Space
NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response
In late January 2013, snow blanketed Great Britain from London in the south to Edinburgh, Scotland, in the north. The image was captured by the The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite. But you knew that.PHOTOS: Green Earth Beauty
NASA image courtesy Jeff Schmaltz LANCE/EOSDIS MODIS Rapid Response Team, GSFC
The Canary Islands appear to have tails made by smooth and choppy water, and the reflection of sunlight. The image was captured by the same satellite that photographed Great Britain under snow. All of these images are in the current Round of 16. Got a favorite?You can't win if you don't play
.PHOTOS: Pyramids Hidden In Satellite Images?
How did Earth's continents first form? A University of Alberta geochemistry PhD student studied a 4-billion-year-old rock and concluded: Look at modern-day Iceland.
The student, Jesse Reimink, collected ancient rock samples from the Acasta Gneiss complex in Canada's Northwest Territories, which contains some of the planet's oldest rocks.
Because they're so old and have undergone so many changes, many of the Acasta Gneiss rocks don't lend themselves to precise geochemical analysis. But some of the ones Reimink collected were preserved well enough to reveal what Reimink called, in a University of Alberta (U of A) article, "crust-forming processes that are very similar to those occurring in present-day Iceland."
Today it's accepted that plate tectonics -- in which pieces of the Earth's crust shift beneath each other into the Earth's mantle and cause magma to rise to the surface -- are responsible for the buildup of continents.
But, Reimink told the U of A, it's not as clear whether plate tectonics existed a couple of billion years ago. One theory holds that the land masses formed in the ocean as liquid magma rose from Earth's mantle and then, over much time, cooled and became a solid crust.
Iceland's crust built up when magma from the mantle rose to shallow waters and incorporated volcanic rocks already in place. Reimink says this makes today's Iceland a good proxy for how continental crust formed in the early life of Earth.
Reimink's 4-billion-year-old rock seems to back up that notion. "This provides the first physical evidence that a setting similar to modern Iceland was present on the early Earth," he told the U of A.