The Earth

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GEOGRAPHY

About earth

  • Earth, our home, is the third planet from the sun. While scientists continue to hunt for clues of life beyond Earth, our home planet remains the only place in the universe where we’ve ever identified living organisms.
  • Earth is the fifth-largest planet in the solar system. It’s smaller than the four gas giants — Jupiter, Saturn, Uranus and Neptune — but larger than the three other rocky planets, Mercury, Mars and Venus.
  • Our planet sits in a small corner of the Milky Way galaxy, 25,000 light-years from the galactic centre and 25,000 light-years away from the rim, according to Universe Today. Our solar system is situated on a minor arm called the Orion-Cygnus arm, which branches off from the Sagittarius arm, one of the galaxy’s two major spiral arms.
  • The Earth’s circumference is 24,901 miles (40,075 kilometres), making it the largest rocky planet in the solar system. Our planet orbits 93 million miles (150,000 km) away from the sun, giving it the right temperature for persistent liquid water on the surface, the only known body to do so.
  • Earth has a diameter of roughly 8,000 miles (13,000 kilometres) and is mostly rounding because gravity generally pulls matter into a ball. But the spin of our home planet causes it to be squashed at its poles and swollen at the equator, making the true shape of the Earth an “oblate spheroid.”

What is earth Made of?

  • Several enormous landforms known as continents exist in various places on the Earth’s surface. The largest continent, which is sometimes known as Afro-Eurasia (though more commonly broken up into Africa, Europe and Asia), has a total area of 32,800,000 square miles (84,950,000 square km), according to the Encyclopaedia of World Geography.
  • North and South America together comprise 16,428,000 square miles (42 million square km), while the frozen continent of Antarctica is 5,405,000 square miles (14 million square km) and the area of Australia is 2,970,000 square miles (7,656,127 square km).
  • Processes below the Earth’s crust cause these continents to move around over geological time periods. Geologists have discovered underground continents buried deep below the surface, and though nobody quite knows how or when they formed, they may be as old as the Earth itself.
  • The Earth’s crust is a thin layer that extends on average around 18 miles (30 km) below our feet, containing mostly silicate and basaltic rocks, according to the U.S. Geological Survey. The mantle is the next layer down, extending to about 1,800 miles (2,900 km) below the Earth’s surface.
  •  A common misconception is that all the rock in the mantle is melted into magma; in fact, most of it is in a highly viscous form that is so thick that it takes millions of years for its movement to become apparent. In the Earth’s centre is a nickel-iron core that is liquid on the outside, down to 1,400 miles (2,260 km), but crushed by incredible pressures into a solid form at the lowest depths.

Earth interior and exterior structure

Interior

  • Earth’s interior is a complex structure of superheated rocks. Most geologists recognize three major layers: the dense core, the bulky mantle, and the brittle crust. No one has ever ventured below Earth’s crust. 
  • Earth’s core is mostly made of iron and nickel. It consists of a solid centre surrounded by an outer layer of liquid. The core is found about 2,900 kilometres (1,802 miles) below Earth’s surface, and has a radius of about 3,485 kilometres (2,165 miles).
  • A mantle of heavy rock (mostly silicates) surrounds the core. The mantle is about 2,900 kilometres (1,802 miles) thick, and makes up a whopping 84% of Earth’s total volume. Parts of the mantle are molten, meaning they are composed of partly melted rock. The mantle’s molten rock is constantly in motion. It is forced to the surface during volcanic eruptions and at mid-ocean ridges.
  • Earth’s crust is the planet’s thinnest layer, accounting for just 1% of Earth’s mass. There are two kinds of crust: thin, dense oceanic crust and thick, less-dense continental crust. Oceanic crust extends about 5 to 10 kilometres (3 to 6 miles) beneath the ocean floor. Continental crust is about 35 to 70 kilometres (22 to 44 miles) thick.

Exterior

  • The crust is covered by a series of constantly moving tectonic plates. New crust is created along mid-ocean ridges and rift valleys, where plates pull apart from each other in a process called rifting. Plates slide above and below each other in a process called subduction. They crash against each other in a process called faulting. 
  • Tectonic activity such as subduction and faulting has shaped the crust into a variety of landscapes. Earth’s highest point is Mount Everest, Nepal, which soars 8,850 kilometres (29,035 feet) in the Himalaya Mountains in Asia. Mount Everest continues to grow every year, as subduction drives the Indo-Australian tectonic plate below the Eurasian tectonic plate. Subduction also creates Earth’s deepest point, the Mariana Trench, about 11 kilometres (6.9 miles) below the surface of the Pacific Ocean. The heavy Pacific plate is being subducted beneath the small Mariana plate. 
  • Plate tectonics are also responsible for landforms such as geysers, earthquakes, and volcanoes. Tectonic activity around the Pacific plate, for instance, creates “Ring of Fire.” This tectonically active area includes volcanoes such as Mount Fuji, Japan, and earthquake-prone fault zones such as the west coast of the United States.

Earth’s Atmosphere

  • Our planet’s atmosphere is 78% nitrogen, with additional 20% oxygen, 0.9% argon and 0.04% carbon dioxide, plus trace amounts of other gases, according to NASA. Most human activity takes place in the lowest atmospheric layer, the troposphere, which extends 5 to 9 miles (8 to 14.5 km) over our heads.
  • Above that is the stratosphere, where clouds and weather balloons fly, going up to 31 miles (50 km) high. This is followed by the mesosphere, which extends up to 53 miles (85 kilometres) high (this is where meteors burn up) and the thermosphere, which extends far out into space, at least 372 miles (600 km) high.  
  • Human activity is greatly affecting climate and weather in the Earth’s atmosphere. By adding excess carbon dioxide, which traps infrared radiation from the sun, human industry is heating up our planet via global warming, leading to large-scale alterations.
  • Those include a rise in average temperatures by around 2.3 degrees Fahrenheit (1.3 degrees Celsius). September 2019 had some of the hottest recorded temperatures all over the Earth.

Earth’s Magnetic Field

  • Earth’s magnetic field is generated by currents flowing in Earth’s outer core. The magnetic poles are always on the move, with the magnetic North Pole accelerating its northward motion to 24 miles (40 km) annually since tracking began in the 1830s. It will likely exit North America and reach Siberia in a matter of decades.
  • Earth’s magnetic field is changing in other ways, too. Globally, the magnetic field has weakened 10 percent since the 19th century, according to NASA.
  • But these changes are mild compared to what Earth’s magnetic field has done in the past. A few times in every million years or so, the field completely flips, with the North and the South poles swapping places. The magnetic field can take anywhere from 100 to 3,000 years to complete the flip.
  • The strength of Earth’s magnetic field decreased by about 90 percent when a field reversal occurred in ancient past, according to Andrew Roberts, a professor at the Australian National University. The drop makes the planet more vulnerable to solar storms and radiation, which could significantly damage satellites as well as communication and electrical infrastructure.
  • “Hopefully, such an event is a long way in the future and we can develop future technologies to avoid huge damage,” Roberts said in a statement.
  • When charged particles from the sun get trapped in Earth’s magnetic field, they smash into air molecules above the magnetic poles, causing them to glow. This phenomenon is known as the aurorae, the northern and southern lights.

The Earth’s surface

  • The Earth is tilted on its axis by 23.4 degrees, meaning that sunlight falls unevenly on the planet’s surface over the course of the year, creating seasonal variation over most of the planet.
  • But different regions experience different variances in sunlight, and so the Earth’s surface is often broken up into three major climatic zones: the polar regions in the Arctic and Antarctic, which start above or below 66 degrees latitude north or south; the middle temperate zones, between 23 and 66 degrees latitude north or south; and the tropical regions, between the Tropic of Cancer, at 23 degrees latitude north, and the Tropic of Capricorn, at 23 degrees latitude south, according to the National Oceanic and Atmospheric Administration.
  • The tallest point above sea level is the peak of Mount Everest. at 29,029 feet (8,848 meters). A crescent-shaped crevasse at the bottom of the western Pacific Ocean known as the Mariana Trench is the deepest spot on our planet, extending down to 36,037 feet (10,984 m).
  • The Nile is the longest river in the world, winding for 4,258 miles (6,853 km) through north-eastern Africa.
  • Lake Baikal in Russia is the largest and deepest freshwater lake, containing 5,521 cubic miles of water (23,013 cubic km) — a volume approximately equivalent to that of all five of the North American Great Lakes combined.

Earth’s Chemical Composition

  • Oxygen is the most abundant element in rocks in Earth’s crust, composing roughly 47 percent of the weight of all rock.
  •  The second most abundant element is silicon, at 27 percent, followed by aluminium, at 8 percent; iron, at 5 percent; calcium, at 4 percent; and sodium, potassium and magnesium, at about 2 percent each.
  • Earth’s core consists mostly of iron and nickel and potentially smaller amounts of lighter elements, such as sulphur and oxygen.
  •  The mantle is made of iron and magnesium-rich silicate rocks. (The combination of silicon and oxygen is known as silica, and minerals that contain silica are known as silicate minerals.)

Earth’s Moon

  • Earth’s moon is 2,159 miles (3,474 km) wide, about one fourth of Earth’s diameter. Our planet has one moon, while Mercury and Venus have none and all the other planets in our solar system have two or more.
  • The leading explanation for how Earth’s moon formed is that a giant impact knocked the raw ingredients for the moon off the primitive, molten Earth and into orbit. Scientists have suggested that the object that hit the planet had roughly 10 percent the mass of Earth — about the size of Mars.

Life on Earth

  • Perhaps the most striking thing about the Earth, and the feature that so far makes it unique throughout the known cosmos, is the presence of living organisms. Some of the oldest evidence of microbial life suggests that it was already widespread on our planet 3.95 billion years ago.
  • Exactly how these microscopic creatures arose remains a mystery, though experts have proposed many theories.
  • Scientists estimate that there are as many as 1 trillion species on our planet, occupying niches that extend from the upper atmosphere to deep below the rocky surface. Bizarre and complex biospheres exist around hydrothermal vents at the ocean’s bottom and in just about every rock and crevice ever explored.
  • Whether this means that organisms exist on the bounty of worlds in our solar system or beyond remains an open question, though the diversity of life on Earth has given scientists hope that life might exist in extreme environments throughout the universe. 

Statistical Data of Earth

Age  of Earth 4550 million years
Mass of Earth  5.976 X 1024 kg.
Volume of Earth 1.083 x 1024 litres
Mean Density of Earth
Mean Density of Earth 5.518 kg/litre
Total Surface Area of Earth  510,065,700 sq.km.

Total Land Area of Earth 148, 647,000 sq.km.

Total Ocean Area of Earth 36, 16, 37,000sq.km (70.9%)
Total Water Area of Earth 361,150,000 sq.km.
Average Density of Earth5.52 (corresponding to the density of water)

Composition of Whole Earth

Iron35%
Oxygen30%
Silicon15%
Magnesium13%
Nickel2.4%
Sulphur1.9%
Calcium1.1%
Aluminium1.1%
Others0.5%

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