What’s the News: In geologists’ traditional view of the middle of the Earth, the solid inner core is gradually growing as more of the liquid core freezes, as the planet continues its billions-of-years-long process of cooling off. But now scientists are suggesting that parts of the solid inner core get so hot that they turn liquid, and that this is all linked to what’s happening in the Earth’s crust—meaning that our the earthquakes, volcanoes, and plate tectonics that we see are connected to the very heart of the planet.
At least 65 people died in an earthquake that struck New Zealand’s second-largest city, Christchurch, yesterday. As the city digs out from the rubble created by the magnitude 6.3 quake, some there are worried the death toll could climb into the hundreds. And as seismologists unravel the details, it’s becoming clear why this quake was so much deadlier than previous seismic events in New Zealand.
Photographs and video from Christchurch, a metropolitan area of nearly 400,000 residents, showed people running through the streets, landslides pouring rocks and debris into suburban streets and extensive damage to buildings. Witnesses told of watching the spire of the iconic Christchurch Cathedral come crashing down during an aftershock. One witness called it “the most frightening thing of my entire life,” and television footage showed a person clinging to a window in the cathedral’s steeple. [The New York Times]
In 2005, the earth cracked open in Ethiopia. Two volcanic eruptions shook the desert, and a 35-mile-long rift opened in the land, measuring 20 feet wide in some places. Now a new study adds weight to the argument that the opening of this crack marks the first step in the formation of a new sea that may eventually separate East Africa from the rest of the continent. Says lead researcher Atalay Ayele: “The ocean’s formation is happening slowly, likely to take a few million years. It will stretch from the Afar depression (straddling Ethiopia, Eritrea and Djibouti) down to Mozambique” [ABC News].
The study, to be published in the journal Geophysical Research Letters, explains that the seismic movements observed in Ethiopia are very similar to the changes wrought by faults and fissures on the seafloor, where the processes that move tectonic plates usually begin.
Seismic data from 2005 shows that the rift opened in a matter of days. Dabbahu, a volcano at the northern end of the rift, erupted first, then magma pushed up through the middle of the rift area and began “unzipping” the rift in both directions, the researchers explained in a statement today. “We know that seafloor ridges are created by a similar intrusion of magma into a rift, but we never knew that a huge length of the ridge could break open at once like this” [LiveScience], says study coauthor Cindy Ebinger.
The active volcanic region in Ethiopia’s Afar desert sits at the boundary of the African and Arabian tectonic plates, which have been gradually spreading apart for millions years; the new study shows that large-scale seismic events can speed up that process. The gradual separation has already formed the 186-mile Afar depression and the Red Sea. The thinking is that the Red Sea will eventually pour into the new sea in a million years or so [LiveScience].
DISCOVER: Meet the New Continent: East Africa
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Image: University of Rochester
Tiny crystals found in an Australian rock formation may be the key to understanding what earth looked like in its very earliest days, researchers say; a new study of 4-billion-year-old crystals seems to indicate that our planet already had plate tectonics, and may have looked much like it does today. Little is known about the so-called Hadean or the ‘hell-like’ period of Earth’s history, which spans the time from Earth’s formation 4.6 billion years ago until about 3.8 billion years ago. The best geological clues of this era come from hard minerals called zircons, which have survived weathering and can be found within younger rocks [Nature News].
An analysis of the Australian rocks showed that minerals trapped within the zircon crystals had formed at a lower temperature and higher pressure than expected for crust of that age…. This suggests that the crystals had been formed in a subduction zone, where one rocky tectonic plate plunges beneath another, showing that plate tectonics was up and running at this time [New Scientist]. Researchers theorized that the minerals formed at lower temperatures because they were saturated in water, a finding inconsistent with earlier images of the earth as covered in boiling seas of magma; subduction zones are cooler than other deeply buried rock formations because they’re chilled by ocean water.
The evolution of minerals on our planet has been propelled by the evolution of life on earth, a sweeping new study demonstrates. While the underlying assumption isn’t new, the study is the first to chart how the emergence of algae and then complex microorganisms gave rise to the 4,300 or so minerals that are now present on earth.
In the early days of the universe, clouds of gas and dust contained all the naturally occurring elements found in the periodic table, but most were too widely dispersed to form minerals; scientists believe there were only about a dozen minerals in the interstellar medium. According to the study, around a further 60 different minerals formed 4.5 billion years ago, as clumps of matter collided and coalesced to begin forming the Solar System. The smaller fragments congealed into larger, planet-sized bodies, where volcanism and the effects of water took the mineral count into the hundreds. The planets Mars and Venus have got this far [Nature News], and have minerals created by hot magma like quartz and zircon.
An international team of bundled-up scientists will soon set off for Antarctica‘s interior in a quest to learn about the continent’s most massive and mysterious mountain range; although the Gamburtsev mountains are as high and mighty as Europe’s Alps, even the tallest peak is buried beneath 2 miles of ice. Now, during the southern hemisphere’s summer, the researchers will investigate how the Gamburtsevs formed in a place where scientists say no mountains should be.
American researcher Robin Bell, who will be making the trek, explains that there are two “easy” ways to form mountains, and neither makes sense in Antarctica: “One is colliding continents, but after they collide they tend to erode; and the last collision was 500-million-plus years ago…. The other way is a hotspot, [with volcanoes punching through the crust] like in Hawaii; but there’s no good evidence for underneath the ice sheet being that hot. I like to say it’s rather like being an archaeologist and opening up a tomb in a pyramid and finding an astronaut sitting inside. It shouldn’t be there” [BBC News].
A slab of bedrock on the shore of Canada’s Hudson Bay may be the oldest piece of the planet ever discovered: Researchers believe the rock is 4.28 billion years old, which would mean that it formed less than 300 million years after the earth itself came together. However, geologists say that considerable controversy remains over the research team’s method of dating the rocks.
Study author Richard Carlson says that if his team is right about the rock’s extraordinary old age, it will change conceptions of how the planet developed its current form, with solid tectonic plates and a stable crust. Says Carlson: “These rocks paint this picture of an early earth that looked pretty much like the modern earth.” … [T]he existence of solid rock 4.28 billion years ago would run counter to the traditional image of the young earth as a roiling cauldron of magma oceans, a view that is falling by the wayside among researchers as more geological data is unearthed [The New York Times].
Researchers have proposed a new theory for how oxygen production was kick-started billions of years ago, when only trace amounts of the gas existed in the Earth’s atmosphere. When continents collided they started a chain reaction, researchers say, that eventually produced a hospitable, oxygen-rich atmosphere. They argue that the tectonic collisions that created the Superia/Sclavia, Nuna, Rodinia, Gondwana and Pangaea supercontinents also formed supermountains, which eroded rapidly, washing vast amounts of nutrients into the oceans. This fuelled explosions of oxygen-producing algae and bacteria [New Scientist].
The Australian researchers say that each collision of tectonic plates caused a bump in oxygen levels, and that studies of modern mountain formation bear out their theory. Other scientists have already shown that the formation and erosion of the Himalayas led to increases in atmospheric oxygen, [study coauthor Charlotte] Allen notes. “Scale up the Himalaya to supercontinental proportions and you have a modern analogue for what we think happened seven major times in earth’s history” [ABC Science]. However, some experts have expressed skepticism regarding the new theory.
According to conventional wisdom, the towering Andes were formed slowly and gradually over 40 million years, as two tectonic plates gradually collided and buckled the earth’s surface. Now a new study is revising that theory, and proposing that the mountain chain burst upwards in a growth spurt between 10 and 6 million years ago, a mere blink of an eye in geological terms.
The new research doesn’t dispute that the mountain range was formed in the collision of two tectonic plates — the dense Nazca Plate that underlies the Pacific Ocean and the lighter South American plate. But it adds a twist, saying that at one point during the long crash the mountains were suddenly freed of a heavy load and shot upwards towards the heavens.