Two weeks ago the drilling rig " Deepwater Horizon " exploded in the Gulf of Mexico. Since then, millions of liters of crude oil have been spilling into the sea every day. The viscous soup now threatens the coasts of the southeastern USA in particular. The damage to the environment can hardly be estimated.
On 20. April the oil platform Deepwater Horizon caught fire, two days later it sank. Eleven workers were killed in the explosion, 115 could be rescued. What looms after this disaster is a devastating oil spill in the Gulf of Mexico. For days now, diving robots have been trying to find the leaks in 15.000 meters deep. But all attempts to stop the leaking crude oil have failed so far. Efforts to prevent the oil spill from spreading also failed to achieve the desired success. High swells, for example, hampered the use of floating barriers to contain the spreading oil slick: The oil continues to drift toward the coast. A state of emergency has already been declared in the U.S. states of Louisiana, Mississippi, Florida and Alabama.
Experts expect billions of dollars in damage. About half of the sum will have to be used to clean up polluted coastlines. Also tremendous losses in tourism and fishing are expected.
After the explosion, the drilling platform is in flames.
Source: imago stock&people 
In the foreground, the oil slick can be seen as a dark spot.
Source: imago stock&people 
Floating barriers are to stop the oil spill
Source: imago stock&people
The danger of deep-sea drilling
A hundred years ago, high-yield oil deposits were comparatively easy to discover and the oil was easy to extract. Today, however, many of these oil wells have already been exploited. But because our energy needs are constantly rising, oil fields that are difficult to access are now also being developed. They include oil deposits in the deep sea, which lie in water more than 500 meters deep. Floating drilling platforms will be set up to access the oil. Raw material is extracted from these drilling platforms – also called "offshore extraction". However, this type of oil extraction involves a great deal of effort and involves high risks, as the Deepwater Horizon accident has shown. But as long as demand continues to rise, oil must be sought deeper and deeper – now in water depths of up to 3,000 meters.
Treasures at the bottom of the sea
Hidden treasures lie deep down on the seabed. We are not talking here about the sunken prey of predatory seafarers; we are talking about raw materials that occur on the ocean floor.
Manganese nodules
Source: imago/blickwinkel
One of these resources is methane hydrate. This combustible ice is stored at a depth of more than 500 meters on the ocean floor. It is formed at low temperature and high pressure from water and methane produced by certain single-celled organisms during metabolism. The estimated reserves of methane hydrate contain more than twice as much carbon as all the world’s oil, natural gas and coal reserves. But whether it can contribute to our energy supply in the future is debatable. Its extraction is difficult because it decomposes easily at higher temperatures, releasing methane. The danger here is that methane is a greenhouse gas. If too much of it gets into the atmosphere, it affects our climate, temperatures rise.
At a depth of about 5,000 meters, there is another strange substance at the bottom of the Pacific: manganese nodules. These black lumps can grow to be about the size of potatoes, some even like heads of lettuce. They are of interest to humans as raw materials because they contain large quantities of the metals manganese and iron. But the wrinkled formations also contain high levels of copper, nickel and cobalt – metals that are needed in the electrical industry and for steel production. Whether their removal is worthwhile still needs to be researched: Although they have a much higher metal concentration than ore mines on land, mining manganese nodules is particularly complicated due to the great ocean depths in which they occur.
From the interior of the earth: ores and dialectical metals
Copper was the first metal discovered by man in the earth’s crust. It could be formed into simple tools or weapons and was so important that an entire era was named after it: the Copper Age. The tools got better when man mixed copper with tin and invented bronze. And when he learned to smelt iron, the triumphant advance of metal tools finally began.
Copper brewing kettle
Source: Colourbox 
Copper ore
Source: Colourbox
Unlike the earth’s core, the earth’s crust consists mostly of nonmetals. Nevertheless, metals such as iron, aluminum, manganese or potassium can be found in its rocks. Experts (geochemists) can determine exactly how often they occur. This is how they found out that about seven percent of the Earth’s crust is made of iron.
Mining iron ore
Source: Colourbox
Like most metals, iron occurs as a chemical compound with other elements, known as ore. To extract iron from ore rock, the ore rock is ground, mixed with coal, and heated. Then a chemical reaction takes place that removes the other elements from the ore, leaving pure, elemental iron.
Some metals, on the other hand, hardly combine with other elements at all. It therefore does not weather and occurs in pure form in the earth’s crust. These "native metals" include gold, silver or platinum. Platinum and gold are also extremely rare: Gold averages only 0.001 grams in a ton of rock. However, a place is only called a deposit when it contains a thousand times the amount of gold – that is, one gram of gold per ton of rock.
Massive cast gold ingots
Source: Colourbox
Rare earth metals" are more common than gold or platinum. What sounds strange has a simple reason: These metals are considered rare because they do not form their own deposits, so they are not concentrated but only scattered. The talk is therefore also of spice metals. Their importance has increased greatly in recent years because they are needed to manufacture electronic devices such as cell phones and computers.
Iron or steel rusts in combination with oxygen and water
Source: Colourbox
The outermost layer of the earth
Like an egg from an eggshell, the Earth is also surrounded by a hard shell. This outermost layer surrounds the earth’s mantle and is called the earth’s crust. If you compare the earth to a peach, the earth’s crust is – relatively speaking – as thick as its skin. Under continents, it reaches an average depth of 40 kilometers, and under the oceans only about seven kilometers.
The earth’s crust is as thick in relation to the earth as the peach skin is to the peach
Source: Colourbox
Beneath it lies the outer part of the Earth’s mantle, which reaches down to a depth of about 100 kilometers. It is also solid, but consists of heavier rock. The earth’s crust and this outermost part of the mantle together are also called the "lithosphere". This solid layer of rock is broken into plates of different sizes that drift very slowly on the hot, viscously flowing mantle of the Earth.
Iceland lies on the mid-Atlantic ridge, where the lithospheric plates diverge
Source: Colourbox
Where the molten rock from the hot mantle penetrates upward, the earth’s crust can break open. Then lava flows out, which becomes new earth crust. It mainly happens where the plates of the lithosphere adjoin each other, such as at mid-ocean ridges.
The Alps – high mountains at the plate boundary
Source: Colourbox
In Iceland, for example, these plate boundaries are clearly visible: Cracks and furrows run through the earth’s crust here, where the Eurasian and North American plates drift away from each other. In the Mediterranean area there is also a plate boundary. Because here the African plate presses against the Eurasian plate, there are in Italy many volcanoes and again and again earthquakes.
The Lipari Islands – a chain of volcanoes in Italy
Source: Colourbox
The crust is covered by the bottom. The soil of the land masses is formed from weathered rock and remains of animals and plants. The seafloor, on the other hand, develops from sediments such as clay and the sunken remains of marine organisms. On the coasts, the seafloor also consists of deposited debris that has been eroded from the mainland and washed into the sea.
Sedimentary rocks
Some rocks look as if they are striated. In the Dolomites, for example, such transverse bands are often clearly visible. Also sandstone or limestone quarries sometimes have similar pretty patterns.
Rugged rock faces in the Dolomites
Source: Colourbox
The "stripe design" is created already during the formation of the rock. The source material is weathering debris carried away by water or wind. Rivers, glaciers and dust storms lose their power at some point: River courses slow down towards their mouths and eventually flow into the sea or a lake. Glaciers advance into warmer regions and melt away. Even dust storms eventually subside. Then they cannot carry dust, sand and debris any further. The crushed rock dragged along settles down. Over time, the deposited material forms an ever higher layer – the sediment. Especially on the seafloor and on the bottom of lakes, where rivers wash up a lot of material, such sediments accumulate, including remains of dead animals or limestone shells.
The individual sediment layers appear like stripes in the rock
Source: Colourbox
Gradually, different sediments are layered on top of each other. For example, one layer may be sandstone: In dry times, the wind has blown desert sand here. When the sea level rises again, this layer is covered by water: calcareous shells of marine animals sink to the bottom of the sea and deposit another layer above the sand. Over millions of years, the climate changed again and again, causing the sea level to fluctuate. This allowed different layers to be deposited.
Sand and remains of living creatures settle on the seafloor
Source: Colourbox
Over time, the sediment cover becomes thicker and thicker. Under the load of their own weight, the initially loose sediments are compressed more and more, small cavities disappear, the mass thickens. Further layers are deposited on top, the sediment becomes more and more solid and finally, under pressure, becomes sedimentary rock. This process is also called diagenesis in geology. If, for example, the shells of tiny marine animals are pressed together to form stone, limestone is formed. Fine grains of quartz sand cement together under the high pressure to form sandstone.
Besides debris, dead animals, for example fish, also settle on the seafloor. Sealed airtight, their bones and scales were preserved and fossilized. Such fossils have perpetuated themselves in the stone. Even after millions of years, they still reveal a lot about the time when the sediment was formed. This is why geologists can read the rock layers like a history book.
Fossils are fossilized living beings
Source: Colourbox
Normally only the top layer is visible to us. However, when a river digs through the sedimentary rock, or it is lifted during mountain building, or blasted free in a quarry, we get a view of the cross-section. The individual sediment layers are then clearly visible as "stripes" or bands in the rocks.
Rocky coastline with a striped look
Source: Colourbox