North America - Geology
The oldest stable core (craton) of the North American
continent is made up of a large Precambrian-Cambrian
continent, Laurentia, where the bedrock is today exposed in
the Canadian Shield and Greenland, while in the interior (Interior
Platform) is covered by younger deposits and basins.
The core area is in the north, east and south surrounded by
Paleozoic folding belts, which are shot over the craton of
the Ellesmeric Folding Belt in northern Canada and
Greenland, the Northern Caledonian folding belt, the
Appalachians and the Ouachita Mountains. The North American
mountain ranges west of the craton developed from Mesozoic
and Tertiary, as seabed dispersal in the then Pacific
brought several oceanic plates obliquely toward subduction
zones off the west coast of North America. Towed crustal
fragments from archipelago and volcanic plateaus and
scrapped seabed formation were displaced along the coast and
united with the continent. From the subduction zones
penetrated intermediate to acidic magmas and solidified in
large intrusions (batholiths), i. in Sierra Nevada, and gave
rise to violent eruptions. Several volcanoes remain active
(for example, in the Cascade Range and the Alaska
Aleutians). In Tertiary, lateral displacement and
compression of the coastal chains continued; in the Basin
Range Province (Great Basin) stretching of the earth's crust
(extension) occurred, with the erosion of large crustal
areas and widespread block rejection. In the
Columbia-Snake-River area and in Mexico, the fold mountains
are overlain by thick basaltic lava flows. The Colorado
Plateau (Grand Canyon) is an isolated remnant from the
craton. In the eastern Rocky Mountains, recess and foreland
deposits have been shot across the Interior Platform.
According to
AbbreviationFinder.org, NA stands for North
America.
Now the Pacific plate itself is brought down into the
subduction zone below Alaska and the Aleuter Arch, and south
of 50 ° N. the scattering zone is close to or below the
continent and is divided by large transformative faults. The
zone is offset sideways along the San Andreas fault, which
has passed it to the Gulf of California. Here it has
"spotted" the California Peninsula of the North American
Plate. Mexico's and Central America's Cordillera branches
into the Andes Mountains of South America and the Caribbean,
where a subduction zone leads the ocean floor from the
Atlantic Ocean below the Caribbean.
Where the North American continent borders the North
Arctic, Atlantic, Davis Strait and Gulf of Mexico, passive
margins have been developed since the Mesozoic, where thick
deposits of land material (clastic sediments) and carbonates
have been deposited. During the Gulf of Mexico and the
coastal plain north of it, evaporites from the Jurassic (c.
206-142 million years) form a large salt- shore province.
Mineral raw materials
North America is rich in mineral resources. The central
shield has ribboned iron ore at Lake Superior and some of
the world's largest gold deposits with gold deposits,
Homestake, at Kirkland Lake, as well as massive sulphide
deposits (Kidd Creek). Also on the shield is the world's
largest nickel deposit, Sudbury. The Palaeozoic folding
belts have in the North Elesmeric lead and zinc deposits,
Polaris, and in the east are Appalachian massive sulfide
deposits, Ducktown. Large sedimentary deposits are
widespread; examples are uranium in sandstone in the
Colorado Plateau and Key Lake, copper, lead and zinc in
clastic sediments (Sullivan, Red Dog) and lead-zinc in
carbonate rocks, the so-called Mississippi Valley type, in
Tennessee. The Mesozoic and Tertiary folding chain along the
west coast of North America has a wealth of mineral
deposits, among others. copper deposits with copper (Bingham
Canyon, Bisbee) and with molybdenum (Climax) and gold
deposits in Nevada. Tungsands gold deposits are known from
gold fever days in California, Alaska and Yukon. North
America is also a major producer of industrial minerals such
as borax from Death Valley.
Central American vegetation
The vegetation is largely determined by the climate. The
Central America is a continent divided into two parts, the
island and the mainland, and features in most of its
territory tropical climates due to its location close to the
equator. The exception is the mountain range that cuts its
continental part in the south-north direction, which
presents cold climates due to the altitude.
The tropical climates are found in the island portion and
the coastal east and west of the mainland. The tropical
savanna is found in the western portion of the great
islands: Cuba, Jamaica, in addition to the Dominican
Republic and Haiti, which share the island of Hispaniola.
This vegetation is characterized by large fields with the
presence of some bushes and flat-topped trees. The tropical
savanna climate has a two-season regime, one dry and the
other humid, forcing the vegetation to adapt to the dry
regime. These adaptations include small, thick leaves and
rough skin, or leaves covered with wax or hair, reducing
plant transpiration and keeping the moisture collected
during the rainy season. Small islands, to the west of the
large islands and the mainland, are dominated by tropical
and equatorial forests. The rainforest climate is extremely
humid and hot throughout the year, which ended up causing a
great differentiation of species in tropical forests, which
have the greatest biodiversity the globe. This diversity is
presented in a canopy of hearts divided into three niches:
the upper, between 50 and 60 meters, medium (the densest),
between 20 and 40 meters, and the lower, between 5 and 15
meters. There is little or no vegetation cover below five
meters, as the canopy is so dense that only 1% of sunlight
can reach the ground. On the western coast of the mainland,
we have the seasonal tropical forest, with a discontinuous
canopy and medium-sized trees, up to 20 meters, and
deciduous, which lose their leaves in the dry season. The
discontinuous canopy and the loss of leaves in the dry
season allow the insolation of the soil and, thus, the
appearance of undergrowth.
Non-tropical vegetation dominates the highest parts of
the mountain range in the center of the continental portion
and in the northwest of the same. In the highest parts we
find the forest of altitude. Unlike the northern coniferous
forest, the Central American forest has more varied species,
with a discontinuous and well-stratified canopy, no more
than 30 meters high. The height and density of the canopy
varies according to the elevation in which the forest is
located, going from a dense forest to a formation of fields
of altitude, with a formation of grasses and low shrubs. The
desert vegetation is found in the northwest of the
continental part, characterized by cacti and xerophyte
shrubs, adapted to the dry climate. Adaptations include long
and capillarized main root, for better absorption of
moisture in the soil, succulent stem to retain liquids, wax
coating and hair, to prevent water loss.
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