Archive for the ‘Geology’ Category
The Earth is about 4,500 million years old. Currently, 75 percent of the continental crust is less than 1,000 million years, and only about 7 percent is composed of rocks of the Archean (over 2,500 million years old).
What is remarkable and perhaps unexpected, is that there is increasing evidence that generated large amounts of continental crust over 2,500 million years. Since continental crust is mostly newer, this implies a high rate of destruction of the primordial crust, which was then replaced by new crust. The chronology of these processes and geodynamic conditions of generation, destruction and renewal of the continental crust are still subjects of considerable debate.
In a recent study, Bruno Dhuime from the University of Bristol, together with colleagues from the Universities of St. Andrews and Portsmouth, all three in the UK, has found that the rate of growth of continental crust of the Earth was high during the first 1,500 million years of history of the planet, and then declined significantly over the next 3,000 million years, that is until today. This sharp decrease indicates a change in the way it was generated and retained the continental crust. Read the rest of this entry »
According to the commonly accepted theory, the first continental crust formed when tectonic plates collided. These collisions led to other barks, the ocean, sinking into the Earth’s mantle, which partially melted to a depth of about 100 kilometers. That later molten rock reached the surface of the Earth and formed the first continents. New research now points to another origin.
Using computers, the team of Thorsten Nagel and Elis Hoffmann of the University of Bonn, and Carsten Munker of the Institute of Geology and Mineralogy at the University of Cologne, both institutions in Germany, simulated, in the light of further analysis, the composition of the bed rock and molten rock to emerge from the partially molten oceanic crust at different depths and temperatures. Then, the investigators compared the data calculated for the rock melted with the real concentration of elements plan in the oldest continental rocks.
The results provide a very different story to that accepted so far: the ocean crust did not have to descend to a depth of 100 kilometers to create fused stony matter which rocks are made of the first continents. According to new calculations, it is more likely a depth of 30 to 40 kilometers, which essentially involves a stay in the crust, without the “reprocessing” in the mantle. Read the rest of this entry »
Researchers at the University of Madrid and the CSIC (Consejo Superior de Investigaciones Cientificas) have applied a three-dimensional laser, a noninvasive technique to map out the effects on a rock collected near the impact crater Karikkoselka meteorite (Finland).
Meteorites (fragments of asteroids that hit the surface of the Earth or another planetary body) are the most important extraterrestrial matter that comes from space by the large amount of mineralogical information provided to us, at partial and temporary processes occurring in the solar system.
On Earth have been cataloged so far, 178 craters and impact structures with diameters ranging from only tens of meters to over 100 km. It is estimated that each year enter the atmosphere about 500 meteoroids greater than 0.5 kilos, although only four of them are recovered as meteorites. Read the rest of this entry »
These have been obtained the first proof that already there were capable bacteria to breathe oxygen lodged in firm land some 100 million years earlier than previously thought. The form of primitive life on land aerobic respiration appeared 2,480 million years ago.
The research team, led by Kurt Konhauser, geomicrobiologist at the University of Alberta, Canada, has achieved this result after investigating a link between levels of atmospheric oxygen and increased concentrations of chromium in ancient seabed rocks. The researchers suggest that the increase in chromium levels was caused by the oxidation of pyrite land. Read the rest of this entry »
A new research will compare the amount of snow during the cold season, and melting of snow and ice that occurs during the warm season in Pyrenean glaciers, and study and its evolution. North Glacier, located in the Ordesa National Park and Monte Perdido in the Pyrenees of Aragon was the first to be scanned in three dimensions.
Researchers at the University of Zaragoza and the Pyrenean Institute of Ecology (IPE-CSIC) have applied a long-range laser scanner for mapping in three dimensions and high spatial resolution, each two feet, the surface of the glacier north.
This glacier from the Ordesa National Park and Monte Perdido is one of the most spectacular examples of the current Pyrenean glaciers. Photographs showing its evolution from the late nineteenth century served as a testimony of the great retreat of glaciers that have experienced the Pyrenees in recent decades. Read the rest of this entry »
Scientists have assumed for some time that the carbon cycle of Earth extends deep inside the planet, but until now there was no direct evidence. The mantle the thickest layer of the Earth is largely inaccessible.
It extends from 10 to 2,900 kilometers below the Earth’s surface. Some researchers, who include specialists from the Carnegie Institute in the U.S., have analyzed diamonds originating in the lower mantle at depths of 700 km or more, and came to the surface in rocks called kimberlites, expelled during volcanic eruptions. Read the rest of this entry »
Almost all oceanic islands are volcanoes. Several, like Hawaii, the material originated from Earth’s mantle.
This geological process begins with the rise of hot rock in cylindrical columns, from a depth of nearly 3,000 kilometers. Near the surface melts, because the pressure is lower, and form volcanoes. The plumes are the result of the rise of oceanic crust material before it sank to the bottom of the mantle in an old stage in the history of Earth. Read the rest of this entry »
Currently, molecular oxygen constitutes 21 percent of the air we breathe, which represents a significant portion of the Earth’s atmosphere. However, in the turbulent primordial gas mixture that characterized the atmosphere of our world in its distant past, there was little molecular oxygen, or maybe even was virtually nonexistent.
It was not until the Great Oxidation, about 2,300 million years, when oxygen started to have an appreciable influence on the atmosphere, stimulating the evolution of air-breathing organisms that were more complex, until finally allow the emergence of life just as we know it today.
Now, new research of MIT suggests that molecular oxygen may have formed on Earth hundreds of millions of years before it passed into the atmosphere, keeping discreetly in a series of ‘oxygen oases’ located in the oceans. Read the rest of this entry »
The ebb and flow of ocean tides is a phenomenon that generally is considered one of the most predictable on Earth. But in reality the scope of the tides varies considerably with the passage of long periods of time, in ways that have not been properly taken into account in most assessments of changes in the level of prehistoric seas.
Due to phenomena such as ice ages, plate tectonics, the processes of land elevation, erosion and sedimentation, the tides have changed dramatically through the millennia, and may change again in the future, as is revealed a new study conducted by the team of David Hill (Oregon State University).
Some tides on the East Coast of the United States, for example, could be several times the past much greater than today, presenting a difference between high tide and low of 3 to 6 meters, instead of the current 1 to 2 meters on average. Read the rest of this entry »
Carbonaceous chondrites are a type of meteorite rich in organic matter and contain samples of the materials involved in the creation of our planet nearly 4,600 million years. In fact, some of these materials probably formed even before our solar system, and could be crucial for the emergence of life on Earth.
The complex set of organic materials in carbonaceous chondrites may vary considerably from one meteorite to another.
New research shows that most of these variations are the result of hydrothermal activity that took place in the first few million years since the formation of the solar system, when meteorites were still part of larger bodies, probably asteroids. Read the rest of this entry »