Versus the ocean evolve rar

Love this track. More Love this track Set track as current obsession Get track Loading. Friday 16 July Saturday 17 July Sunday 18 July Monday 19 July Tuesday 20 July Wednesday 21 July Thursday 22 July Friday 23 July Saturday 24 July Sunday 25 July Monday 26 July Tuesday 27 July Wednesday 28 July Thursday 29 July Friday 30 July Saturday 31 July Sunday 1 August Monday 2 August Tuesday 3 August Wednesday 4 August Thursday 5 August Friday 6 August Saturday 7 August Sunday 8 August Monday 9 August Tuesday 10 August Wednesday 11 August Thursday 12 August Friday 13 August Saturday 14 August Sunday 15 August Monday 16 August Tuesday 17 August Wednesday 18 August Thursday 19 August Friday 20 August Saturday 21 August Sunday 22 August Monday 23 August Tuesday 24 August Wednesday 25 August Thursday 26 August Friday 27 August Saturday 28 August Sunday 29 August Monday 30 August Tuesday 31 August Wednesday 1 September Thursday 2 September Friday 3 September Saturday 4 September Sunday 5 September Monday 6 September Tuesday 7 September Wednesday 8 September Thursday 9 September Friday 10 September Saturday 11 September Sunday 12 September Monday 13 September Tuesday 14 September Wednesday 15 September Thursday 16 September Friday 17 September Saturday 18 September Sunday 19 September Monday 20 September Tuesday 21 September Wednesday 22 September Thursday 23 September Friday 24 September Saturday 25 September Sunday 26 September The Earth's unchanging size implies that the crust must be destroyed at about the same rate as it is being created.

Such destruction recycling of crust takes place along convergent boundaries where plates are moving toward each other, and one plate sinks is subducted under another. The location where sinking of a plate occurs is called a subduction zone. The type of convergence some call it a very slow "collision" that takes place between plates depends on the kind of lithosphere involved. Convergence can occur between an oceanic and a largely continental plate, or between two largely oceanic plates, or between two largely continental plates.

Convergence between continental and oceanic crust. Subduction processes in oceanic-oceanic plate convergence also result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes are typically strung out in chains called island arcs. As the name implies, volcanic island arcs, which closely parallel the trenches, are generally curved.

The trenches are the key to understanding how island arcs such as the Marianas and the Aleutian Islands have formed and why they experience numerous strong earthquakes. The descending plate also provides a source of stress as the two plates interact, leading to frequent moderate to strong earthquakes. Not all plate boundaries are as simple as the main types discussed above.

In some regions, the boundaries are not well defined because the plate-movement and deformation occurs over a broad belt called a plate-boundary zone. One of these zones marks the Mediterranean-Alpine region between the Eurasian and African Plates, within which several smaller fragments of plates microplates have been recognized.

Because plate-boundary zones involve at least two large plates and one or more microplates caught up between them, they tend to have complicated geological structures and earthquake patterns. The cause of plate movement is not accessible to direct observation. The various features of plate movement, and the increased heatflow along midoceanic ridges are consistent with the idea that plate movement is caused by convection in the mantle.

The driving force behind the convection is heat generated by radioactive decay in the earth. The heat released by this decay radiogenic heat is transferred by convection slow movement of hot, plastic rock to the surface of the earth. Heat production in the earth will cease as radioactive decay diminishes, and then convection will cease and the final cooling phase of the Earth will begin.

No more mountain ranges will be built, and the continents will become very flat. Eventually the oceans may cover the continents again shallow seas, buildup of carbonate platforms, change of seawater composition because terrestrial input cut off, possibly a new stage in evolution.

Tectonic movements will still occur, but this time they will mainly be a response to differential cooling of the earth surface already cold, but interior shrinks now as well, volume reduction, pressure ridges will form due to shrinking, may resemble folded mountain belts. Most of the earth's surface is covered by oceans, but for a long time the oceans have been an essentially white spot on the map of the world.

Early expeditions like that of the Beagle Charles Darwin brought some preliminary knowledge, compilations of data by ship captains brought some initial knowledge about ocean currents and migration of fish swarms mention Melville, Captain Ahab , but by and far we did not know much about the topography of the ocean floor, much less about its geological features.

Starting at around , however, a vast amount of knowledge has been gathered about the oceans, about their water chemistry, the cycling of elements, biological aspects, bathymetry, bottom sediments and their stratigraphy. Though much less spectacular and not as well publicized, the progress in knowledge about the oceans is far more important for the future of mankind than to send a few men to the moon. Ocean research has implications for food resources, the supply of raw materials for a growing population, and possibilities of ocean population by man giant raft cities in shallow seas, platforms moving with food-rich ocean currents, etc.

Even populating the deep sea is probably cheaper and more feasible than to have people live in colonies on the moon. Work on the bathymetry of the ocean basins mainly with echo-sounding devices has revealed many morphologic features that were previously unknown, such as oceanic ridges, abyssal plains and hills , seamounts, trenches, and continental margins, all of these features are now easily explained by plate tectonics.

The oceanic crust is not simply a pile of basalt, but can be subdivided into several distinct layers, that form in response to the processes operating at a midoceanic ridge. That the oceanic crust is layered has been known from seismic refraction data, but nobody has ever drilled through the oceanic crust too hot.

Fortunately, once in a while bits and pieces of oceanic crust are incorporated into the uplifted material of flooded mountain belts, and is thus available for direct and detailed study. In Iceland, where the Mid-Atlantic Ridge rises above the sea surface, is another opportunity to examine the structure of the oceanic crust.

As new oceanic crust forms at mid-oceanic ridges, cold sea water invades the hot new crust through the abundant fractures crustal extension. As the sea water heats up its density decreases and it rises upwards.

When it leaves through fractures at the seafloor we have submarine hot springs , better known as black smokers. These hot springs have created quite a bit of excitement in the scientific community because they open up all sorts of unexpected angles on the chemistry of the oceans, the transfer of chemical elements between the oceans and the oceanic crust elemental cycles , and the origin of life. The latter was prompted by the discovery of unusual communities of microbes, worms, clams, and crustaceans that live at hot spring sites and instead of sunlight depend on energy supplied by the hot springs in the form of sulfides.

The characteristic features of continents are shield areas, stable platforms, and folded mountain belts introduced earlier in this lecture. With the theory of plate tectonics we can now relate these features to each other and describe them as different phases in the evolution of continents. Pertinent features of the continental crust are: It consists overall of material with granitic composition granites and gneisses of granitic composition, other compositional rock types, such as basalts are present, but volumetrically not important From the travelling velocity of seismic waves in the continental crust we know that the lower portions of the continental crust are denser than the upper portions, probably because of a downwards increase of rocks of more basaltic composition Continental crust is thickest beneath mountain ranges root zones, km , elsewhere the thickness is about 30 km.

The structure of the continental crust is considerably more complex than the simple layer structure of the oceanic crust. It consists of intensely deformed metamorphic rocks derived from sediments and volcanic rocks that are intruded by granites, and may have been partially remolten to granites.

The oldest continental crust has been determined to be about 3. They cover nowadays about one third of the earth's surface, but initially the proportion of the oceans may have been much larger.

The continental crust is the end product of planetary differentiation accumulation of light materials , and within the crust of each continent we can distinguish three basic components: shields, stable platforms, folded mountain belts. SHIELDS contain the bulk of the rock record of continental evolution and growth, and are thus the key to the understanding of the origin of continents.

As noted earlier, they are essentially flat and consist of a complex arrangement of igneous and metamorphic rocks. The mere fact that these rocks are exposed at the surface now, implies that many kilometers of rock were eroded from the continent before these rocks finally came to the surface. If the shield rocks of a continent are studied with respect to their metamorphic age, it often turns out that those on the center are the oldest ones, and that there are several belts of metamorphic rocks that get progressively younger outward.

The oldest portions of the shields consist of a mixture of volcanic rocks basalts, andesites and volcanic derived sediments erosion of volcanoes , and the rocks show similarity to the material accumulating in modern day island arcs. We know now that his shortening is a direct reflection of the compressive stress regime and subduction of oceanic crust along convergent plate margins, but before plate tectonics the missing crust was very troublesome thing to explain.

The location of these fold belts along continental margins implies that by convergence of plates material is piled up along the continents, and finally becomes part of the continental crust.

Fold belts that are terminated abruptly at the continental margin, such as the Appalachians and the Caledonides, suggest that he fold belts were once much longer, and have been separated when continents broke up by continental rifting. Formation of a fold belt and a metamorphosed root zone on convergent plate boundaries is also known as orogeny or creation of mountain ranges.

We can use these different types of orogenies and the underlying plate tectonic processes to explain the evolution of continents and the continental crust. Crustal recycling and the differentiation of the continental crust is intimately related to the composition of the oceans, the supply of nutrients for the global biomass, and thus is also linked to those global feedback mechanisms that we consider essential for climate regulation carbon cycle etc.

In part, the biosphere has adapted opportunistically to whatever chemical components were provided in the process, but it also has an active role through the weathering of continents, the deposition of carbonate banks, the carbon cycle feedbacks with climate, etc.

I hope that in the course of this lecture you have gained insights into three topical complexes: the Earth system really is highly complex, and consists of many nested and interlinked element cycles and feedback loops we are a long way from understanding how the Earth system works in detail, but we are making progress the biosphere is an important component of the Earth system.

Simply through evolutionary selection pressures it may have evolved to participate in climate regulation for most of Earth history. Eventually, all things merge into one, and a river runs through it. The river was cut by the world's great flood and runs over rocks from the basement of time.

On some of the rocks are timeless raindrops. Under the rocks are the words, and some of the words are theirs. I am haunted by waters.

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