Geology is the science and study of the solid Earth and the processes by which it is shaped and changed. Geology provides primary evidence for plate tectonics, the history of life and evolution, and past climates. In modern times, geology is commercially important for mineral and hydrocarbon exploration, is publically important for predicting and understanding natural hazards, plays an essential role in geotechnical engineering, and is a major academic discipline.

Geology of Europe

The geology of Europe is varied and complex, and gives rise to the wide variety of landscapes found across the continent, from the Scottish Highlands to the rolling plains of Hungary. Europe’s most significant feature is the dichotomy between highland and mountainous Southern Europe and a vast, partially underwater, northern plain ranging from England in the west to the Ural Mountains in the east. These two halves are separated by the Pyrenees and the AlpsCarpathians mountain chain. The northern plains are delimited in the west by the Scandinavian Mountains and the mountainous parts of the British Isles. The southern mountainous region is bounded by the Mediterranean Sea. Major shallow water bodies submerging parts of the northern plains are the Celtic Sea the North Sea, the Baltic Sea complex and Barents Sea.

Components

Europe consists of the following cratons and terranes and microcontinents:

Cannes, France

Geologic timeline

~2300-2200?? Ma Baltica The Baltic Shield (Fennoscandia) was formed from five province blocks: Svecofennian, Sveconorwegian, Karelian, Belmorian and Kola,
2300-2100 Ma Baltica The Sarmatian craton was formed from other blocks,
???? Ma Baltica The Volgo-Uralia shield was formed,
1900-1800 Ma Baltica The East European craton (≈ Baltica) was formed from the above three cratons, to become a part of the supercontinent Columbia,
~1500 Ma Baltica The Nena Continent composed of Arctica, East Antarctica and Baltica, was splitoff from Columbia,
???? Ma Baltica East Antarctica was shaved off from Nena,
~1100 Ma Baltica Baltica and Arctica, now part of a Laurentia block, was joined to Rodinia,
~750 Ma Baltica The Baltica/Laurentia block, AKA Proto-Laurasia, was shaved off the splitup Rodinia,
~550 Ma Baltica Proto-Laurasia broke apart, forming Baltica and Laurentia,
~530 Ma Avalonia Avalonia broke off from Gondwana by rifting
~450 Ma Avalonia Avalonia came in contact with Baltica
~440 Ma Balt./Aval. Laurentia and Baltica collided to form Euramerica, Avalonia attached to the eastern coast of Laurentia,
~350 Ma Balt./Aval. Euramerica collided with Gondwana forming Pangea, while Avalonia was squished to a narrow strip in between Gondwana and Laurasia,
~300 Ma Balt./Kaza. Siberia and Kazakhstania were the last continents to adjoin Pangea towards the Baltica block, thereby forming a Laurasia subcontinent of Pangea,
~270 Ma Cimmeria The Cimmerian Plate split off from Gondwana by rifting,
~190 Ma Baltica Laurasia split off from Gondwana by the widening of the Atlantic Ocean, and very soon afterwards split into Laurentia (North America) and a Eurasian continent.
50 Ma — present As the continents approached their present configuration, Europe experienced periods of land connection to North America via Greenland, resulting in colonization by North American animals. During these times, higher than present sea levels sometimes fragmented Europe into island subcontinents. As time passed, sea levels fell, with seas retreating from the plains of western Russia, establishing the modern connection to Asia. Asian animal species then colonized Europe in large numbers.

Other places on the world

Antigua

Cooper Mountain, Colorado

Physical Features of the  Ocean

Beneath the world’s oceans lie rugged mountains, active volcanoes, vast plateaus and almost bottomless trenches. The deepest ocean trenches could easily swallow up the tallest mountains on land.

Around most continents are shallow seas that cover gently sloping areas called continental shelves. These reach depths of about 650 feet (200 m). The continental shelves end at the steeper continental slopes, which lead down to the deepest parts of the ocean.

Beyond the continental slope is the abyss. The abyss contains plains, long mountains ranges called ocean ridges, isolated mountains called seamounts, and ocean trenches which are the deepest parts of the oceans. In the centers of some ocean ridges are long rift valleys, where Earthquakes and volcanic eruptions are common. Some volcanoes that rise from the ridges appear above the surface as islands.

Other mountain ranges are made up of extinct volcanoes. Some seamounts, called guyots, are extinct volcanoes with flat tops. Scientists think that these underwater mountains were once islands but their tops were worn away by waves. The diagram below shows the main features found on the ocean floor.

Oceanographers know these features exist because much effort has been spent on mapping the ocean bottom. In order to make maps of the ocean floor, the depth of the ocean must be known in many places. In the early days of ocean exploration, sailors made depth determinations called soundings by means of a lead line. This was simply a long piece of rope, marked off in fathoms (six-foot intervals) and having a lead weight at one end. The depth was measured by dropping the weight into the water and noting how much line went out when the lead weight reached the bottom.

Taking soundings this way is time-consuming, especially in deep water. Today most depth measurements are made using an echo sounder. Instead of dropping a weight, a pulse of sound energy is transmitted electronically toward the bottom. The time it takes the pulse to travel to the bottom and be reflected back up to the surface is measured. From this time interval, the depth of the water can be calculated. When pulses are sent out and received in quick succession, an almost continuous recording of the ocean depth called a bottom profile may be obtained.

The sedimentary rocks that exist on the ocean bottom are much younger than any similar rocks found on the continents. The cores of mud and rock brought back by deep-sea drilling ships vary greatly in age, but no deposits from the ocean floor seem to be more than about 200 million years old. This makes oceanic crust very young compared with the continents, which contain rocks up to about 4 billion years old.

Plate Tectonics

Earth’s outer shell, the lithosphere, long thought to be a continuous, unbroken, crust is actually a fluid mosaic of many irregular rigid segments, or plates. Comprised primarily of cool, solid rock 4 to 40 miles thick, these enormous blocks of Earth’s crust vary in size and shape, and have definite borders that cut through continents and oceans alike. *[Oceanic crust is much thinner and more dense than continental, or terrestrial crust].

There are nine large plates and a number of smaller plates. While most plates are comprised of both continental and oceanic crust the giant Pacific Plate is almost entirely oceanic, and the tiny Turkish-Aegean Plate is entirely land. Of the nine major plates, six are named for the continents embedded in them: the North American, South American, Eurasian, African, Indo-Australian, and Antarctic. The other three are oceanic plates: the Pacific, Nazca, and Cocos.

The relative small size of the numerous other plates neither diminishes their significance, nor their impact on the surface activity of the planet. The jostling of the tiny Juan de Fuca Plate, for example, sandwiched between the Pacific and North American Plate near the state of Washington, is largely responsible for the frequent tremors and periodic volcanic eruptions in that region of the country.

In May of 1980, scientists monitoring Mount St. On May 18, 1980, in Washington state, Mt. St. Helens erupted with the force comparable to that of a hydrogen bomb. The explosion blew off 1,300 feet of the mountain’s top and sent ash and debris more than 12 miles into the sky covering three states – Washington, Oregon, and Idaho. Sixty two people were dead, beautiful forests and lakes were destroyed resulting in $3 billion worth of damage.

Mt. St. Helens had remained dormant for 123 years. In March of 1980 scientists recorded seismic tremors from the mountain. State officials ordered the residents of the area to evacuate and warned people not to hike in the area. However, not everyone took heed to the warnings. Harry Truman, an elderly man living near the mountain, refused to vacate his home. Within minutes of the explosion he and his home, along with other people and homes, were virtually buried in mud. Thousands of acres of timber fell over like match sticks. Lakes clogged with mud. Spirit Lake, adjacent to the mountain, turned into a mud hole and was littered with timber. The eruption caused total devastation to the land, lakes, and forests. Miles away, the city of Yakima, Washington – population of 65,000- was affected the worst.

It was a typical spring day with the birds chirping and the sun shining. However, this typical day did not last long. About 10:00 a.m. a black cloud covered the city and „snowed” ash. Neither a street light nor a neighbor’s porch light could be seen as the ash was so heavy it sank swimming pool covers and caved in old roofs. Businesses and schools were closed down and all normal activity in daily life ceased to exist. Yakima was hit like a snowstorm and it looked like it from afar.

When the ash stopped coming down and the cloud clover lifted it remained gray and dreary for days. Everywhere you looked people wore surgical masks (to keep from breathing the ash in) and swept ash off their rooftops. Any movement stirred up clouds of dust. The city was a mess, but like any disaster life moves on and people cope. Yakima was only inconvenienced by huge amounts of ash and clean up, while the people and the land near the mountain suffered total death and destruction. The fatality rate for Mt. St. Helens could of been much higher if not for the evacuation orders and the advances of technology.

The resulting ash eruption rose an amazing 16 miles into the atmosphere and dropped 500 million tons of ash – enough to cover an area the size of a football field 150 miles deep with ash. Temperatures from the blast exceeded 800 degrees Fahrenheit and within minutes the devastation obliterated homes, highways and wildlife. One man who refused to leave his home on Mount St. Helen, Harry Truman, was buried under 300 feet of the new level of Spirit Lake. The fury of the Mount St. Helen blast was attributed to the complex interactions between the Pacific Plate, North American Plate, and tiny Juan de Fuca plate, an area known as a triple plate junction.

How Plates Move

Powered by forces originating in Earth’s radioactive, solid iron inner core, these tectonic plates move ponderously about at varying speeds and in different directions atop a layer of much hotter, softer, more malleable rock called the athenosphere. Because of the high temperatures and immense pressures found here, the uppermost part of the athenosphere is deformed and flows almost plastically just beneath the Earth’s surface. This characteristic of the athenosphere to flow allows the plates to inch along on their endless journeys around the surface of the earth, moving no faster than human fingernails grow.

One idea that might explain the ability of the athenosphere to flow is the idea of convection currents. When mantle rocks near the radioactive core are heated, they become less dense than the cooler, upper mantle rocks. These warmer rocks rise while the cooler rocks sink, creating slow, vertical currents within the mantle (these convection currents move mantle rocks only a few centimeters a year). This movement of warmer and cooler mantle rocks, in turn, creates pockets of circulation within the mantle called convection cells. The circulation of these convection cells could very well be the driving force behind the movement of tectonic plates over the athenosphere.





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