In the beginning, and for several hundred million years thereafter, the climate and surface temprature of Earth made it impossible for life to form. However, when its lava-like surface began to cool, hardened surfaces took shape and volcanos began to form.
When a volcano erupts, ammonia, water vapor, and other gases are spewed into the atmosphere. With help from the sun, the ammonia molecules are broken down and in turn release nitrogen, forcing the harmful carbon dioxide and helium gases out of the atmosphere and giving Earth the opportunity to support life. The current levels of nitrogen and oxygen exist today because of this perpetual process.
Modern climates vary depending on their location on the earth. According to the National Snow and Ice Data Center (NSIDC), climate is defined as a synthesis of weather conditions in a given area, charactedized by long-term statistics (mean values, variances, probablilities of extreme values, etc.) of the meteorogical elements in that area.
Basically, climate is an average measurement of precipitation, temperature, wind, and pressure over an extended period of time, most often around 30 years.
The most common climate classification system used today was created by German scientist Wladimir Peter Koppen in 1920. Koppen’s system classifies climates based on precipitations and temperatures. The five major climates are Tropical Moist Climates (A), Dry Climates (B), Moist Subtropical Mid-Latitude Climates (C), Moist Continental Mid-Latitude Climates (D), and Polar Climates (E).
When the major climates are broken down further, they have a code of two or three letters, each letter representing a characteristic of that particular climate. For example, Af indicates a Tropical Rainforest climate, meaning that all twelve months have an average precipitation of at least 2.4 inches.
Tropical Moist Climates
Tropical moist climates extend northward and southward from the equator to about 15 to 25° of latitude. In these climates all months have average temperatures greater than 18° Celsius. Annual precipitation is greater than 60 inches.
Because of intense surface heating and high humidity, cumulus and cumulonimbus clouds form early in the afternoons almost every day. Daily highs are about 32° Celsius, while night time temperatures average 22° Celsius.
The most obvious climatic feature of this climate is that potential evaporation and transpiration exceed precipitation . These climates extend from 20 - 35° North and South of the equator and in large continental regions of the mid-latitudes often surrounded by mountains.
Grassland and true desert, when combined comprise of approximately 26% of the Earth’s land surface.
Moist Subtropical Mid-Latitude Climates
This climate generally has warm and humid summers with mild winters. Its extent is from 30 to 50° of latitude mainly on the eastern and western borders of most continents. During the winter, the main weather feature is the mid-latitude cyclone .
Moist Continental Mid-Latitude Climates
Moist continental mid-latitude climates have warm to cool summers and cold winters. The location of these climates are further north than Moist Subtropical Mid-Latitude Climates.
The average temperature of the warmest month is greater than 10° Celsius, while the coldest month is less than -3° Celsius. Winters are severe with snowstorms, strong winds, and bitter cold from Continental Polar or Arctic air. masses .
Polar climates have year-round cold temperatures with the warmest month less than 10° Celsius. Polar climates are found on the northern coastal areas of North America, Europe, Asia, and on the landmasses of Greenland and Antarctica.
Today the Earth’s surface is comprised of approximately 361,800,000 square kilometers of water and 148,300,000 square kilometers of land. This works out to about 70 percent water and 30 percent land. The highest point on Earth’s crust is Mount Everest at 29,029 feet, while the lowest is the Mariana Trench at 36,200 feet below the Pacific Ocean’s surface.
Such extreme differences in altitude are a result of the Earth’s tectonic plates which cover the outermost surface layer. This outermost layer is called the lithosphere, and is comprised of two parts, a thin outside layer of solid rock called the crust and the rigid upper section called the mantle.
Under the Surface
Although it feels like the Earth is solid to its core from a vantage point on the surface the Earth’s crust is in fact drifting on gooey molten rock called the asthenosphere. The tectonic plates make up the lithosphere and are constantly shifting right above the asthenosphere. Three things can happen - the plates can either collide, they can move apart, or they can slide past each other.
When two or more plates move apart from each other it is called a divergent boundary. Divergent boundaries cause rifts, and volcanic islands which form when the lava flows into the gap created by the two plates and rises above the Earth’s surface. Convergent boundaries are formed when two or more plates collide. Mountain ranges are often formed during this seismic event; one such range is the Himalayas in Asia. Transform boundaries occur when two or more plates slide past each other.
Along with the shifting of tectonic plates, other factors play into the Earth’s changing surface - gravity, water, and wind. Of these main sources water seems to be the leader in changing the surface. This is likely due to the fact that Earth's surface is mostly covered by water.
Koppen System is the most widely used system in identifying climates.
Climate is an average measurement of precipitation, temperature, wind, and pressure over an extended period of time, most often around 30 years.
The Earth’s surface is comprised of constantly shifting tectonic plates.
Other contributing factors for changes in Earth’s surface include gravity, water, and wind.
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