GEOLOGICAL STRUCTURE . Unlike South America, millions of years ago was part of Gondwana, North America – a fragment of Laurasia – the Ancient continent of the Northern hemisphere. The basis of North America is a long Precambrian North American platform . In the North-East of its crystalline basement, composed of granite and gneiss, comes to the surface in the Canadian shield . In the rest of offset by a strong Foundation layer of sedimentary rocks (Sandstone, limestone).
From all sides of the platform in different geological time were “Built” folded area. In particular, strong folding formed on the approach to the site of the Pacific – North American lithospheric plates .
More than 10 thousand years ago the climate of the Northern hemisphere was much more severe: snow fell during the long winter, not had time to melt and accumulate. Gradually it turned into ice. As a consequence, on the North of the continent was formed by a giant glacier covering. Hundreds of years he moved to the South along the uneven surface of the continent. In ice versely large and small fragments of rocks (boulders, gravel, sand, clay), which moved along with the glacier. Moved South, the glacier stopped and the warming climate melted slowly. In areas where there were glaciers that formed glacial landforms.
Fig. Earth crust of North America
The bridge between the continents
Interestingly, only 30 thousand years ago on the Bering Strait was the isthmus that North America was connected to Eurasia. The existence of such a “bridge” between two of the continent is confirmed by the similarity of their flora and fauna.
Fig. Ancient glaciation of North America
RELIEF . In General, the terrain similar to North America terrain of South America. In North America, also in the West tower mountains and widespread in Eastern great plains.
Plains , lying on the platforms occupy the entire Eastern part of the continent. The largest among them – the Laurentian upland is located in the North and a wide strip surrounds the Hudson Bay. To the South are the Central plains . having a hilly surface. Thousands of kilometers from North to South stretched the Great plains. In the direction of the mountains in the West they climb the giant stairs. On the surface of the plains of the ancient glacier that last covered the area, created glacial landforms – polished rocks, hills with rounded peaks, the accumulation of large boulders, Plowed basin. In the South of the continent is lowland Prymeksykanskiy W flat, very boggy surface, densely cut by river valleys.
Mountains occupy only a third of the continent. They are confined to the orogen. Appalachian – Fold-hat mountain, violating the General plainness in the East of the continent. They are old age, so much destruction and low. Their gentle slopes and rounded peaks.
The Cordillera is One of the largest on the planet folded mountain systems. They stretch from North to South through the whole continent 9 000 km away. This powerful mountain belt continues in South America in the Andes. The highest peak of the Cordillera is mount McKinley (6 193 m). It is located in the Northern part of the mountains, where the peaks are covered with snow and glaciers. Cordillera stretching several parallel ridges and consist of different high mountain ranges. East forms a chain of ridges of the Rocky mountains . In the inner parts of the Cordillera are numerous plateaus and plateau, the Great Basin, Colorado, Mexican . They are dissected by deep river valleys called canyons . The Cordillera mountains are young, their formation continues today. In the mountains there are many active and extinct volcanoes. The highest of them – Orizaba and Popocatepetl – rise above 5 000 m. In the Rocky mountains extended geysers, hot springs, mud volcanoes.
Fig. The conquest of mount McKinley
Yellowstone Yellow stone
In 1871 the Rockies “for the use and enjoyment of the people “had created the world’s first national Park – Yellowstone. There are more than 200 geysers. The highest of them is the Steamboat geyser, which ejects water to a height of over 100 m. the Greatest “water content” is the Giant geyser, which at one time throws up almost 38 thousand hectoliters of water. Striking and puddles of boiling mud, colored green due to algae that live in them.
Work with the map
1. Name the most plain. To which the height of the plains they belong to?
2. Where are the mountains? Which ones above?
3. What is the highest altitude are the Appalachian mountains? To which they belong the height of mountains?
4. In what part of the Cordillera posted the highest peak?
5. What minerals are deposited on the plains?
6. What minerals are mined in the mountains?
MINERALS . Minerals in North America found throughout the property. In the North there are large deposits of iron, copper, Nickel, uranium and polymetallic ores. They are all associated with igneous rocks of the Canadian shield.
In sedimentary rocks overlain by platform deposits of coal, oil, natural gas, and various salts. Big oil region located in the Great plains, Alaska, offshore Gulf of Mexico. The largest deposits of coal are concentrated in the foothills of the Appalachian mountains and the Rocky mountains.
Cordillera as rich in sedimentary and igneous resources. In California and Alaska are world famous for gold deposits.
Questions and tasks
1. Install similarities and differences in the geological structure of North and South America.
2. Explain the location of major landforms in North America. Why Cordillera is located in the West of the mainland?
3. What landforms on the plains of ancient glaciers formed?
4. What minerals confined to the ancient sedimentary rock platform?
5. What does the presence of volcanoes, geysers, hot springs in the Cordillera?