Earth’s Atmosphere, Climate, and Biodiversity

Posted on Dec 9, 2024 in Geology

Earth’s Atmosphere: Composition and Function

The atmosphere is the **gaseous layer that surrounds the Earth**. It consists of a mixture of gases arranged in concentric layers of different thickness and density. This protective cover acts as a thermal regulator and regulates complex mechanisms, balancing ecosystems.

Atmospheric Composition

  • The atmosphere is composed of a homogeneous mixture of gases, suspended particles, and liquid droplets.
  • It consists mainly of **nitrogen (78%) and oxygen (21%)**.
  • The remaining 1% consists mainly of water vapor, argon, and carbon dioxide.
  • Other gases present in smaller quantities include neon, nitrous oxide, helium, hydrogen, krypton, xenon, and carbon monoxide.

Weather vs. Climate

“The **weather** is the state of the atmosphere at a given time. It is defined by various weather elements.” A **weather element** is a property or condition of the atmosphere at a given time, e.g., **temperature, pressure, cloudiness, wind, humidity, and rainfall.**

“The climate is determined from the weather for a given area, developed on the basis for a long enough period. To define the climate of a place, the same elements that define the weather are considered, but based on lengthy observations (no more than 10 years) and working with the averages of the data.”

Heat and Temperature

“**Heat** is a form of energy and is measured in units of energy, such as calories or joules. **Temperature** is not a form of energy; it is a measure related to the agitation of the particles forming the body (thermal state) and is measured in specific units such as degrees Celsius (ºC).”

Factors Influencing Air Temperature

  • **Latitude:** The primary source of heat for our planet is solar radiation. At the poles, the sun’s rays arrive at a steep angle, so the amount of solar radiation is much lower than at the equator, where the sun’s rays are perpendicular. Temperature decreases from the equator to the poles.
  • **Altitude:** The higher the altitude, the lower the temperature.
  • **Distance to the Sea:** The sea temperature increases or decreases more slowly than land. This means that in areas near the sea, summers are not as hot and winters are not as cold. The sea acts as a moderator of temperature.
  • **Ocean Currents:** These are movements of large bodies of water in the oceans. They can be hot or cold and modify the temperatures of the areas they cross.

Climatic Factors

“The various physical factors that influence the climate are called **climatic factors**. According to their origin, they include:”

  • **Astronomical** (solar radiation)
  • **Geographical** (latitude, altitude, topography, land distribution, and distance to the sea)
  • **Dynamic** (ocean currents)

Major Climate Types

There are four major types of climate: **hot, temperate, cold, and desert**.

Warm Climates

Warm climates comprise a large area between the Tropics of Cancer and Capricorn. They are characterized by high temperatures that are constant throughout the year. Within this group, there are four subtypes:

  • **Equatorial:** Encompasses a strip north and south of the equator. It is characterized by high thermal uniformity, high temperatures, little difference between seasons and between day and night (whose duration is almost the same), and abundant rainfall.
  • **Tropical:** Characterized by high temperatures and rainfall concentrated in summer. The contrast between seasons is greater than in the equatorial climate.
  • **Subtropical with a Dry Season:** The main feature is dry summers with high temperatures and clear skies. They are found in the lands bordering the Mediterranean, in the valley of California, and in central Chile.
  • **Subtropical without a Dry Season:** Rainfall occurs throughout the year due to the action of the trade winds. In South America, it encompasses southern Brazil, a part of Uruguay, and northeastern Argentina.

Temperate Climates

Temperate climates cover the areas between parallels 40º and 70º North and South latitude in both hemispheres. The average annual temperature is below 18ºC. There are three subtypes:

  • **Oceanic:** It is mild, wet, and windy, with predominantly westerly winds.
  • **Continental:** Characterized by a contrasting thermal regime and low temperatures in winter. Summers are rainy, and winters are dry. It covers large areas of North America, Europe, and Asia.
  • **Transition:** The average annual temperature is around 16ºC. Although winters are less rainy than summers, they are not dry.

Cold Climates

Mean annual temperatures in cold climates do not exceed 5ºC. Within this group, we find the following subtypes:

  • **Polar:** This is the characteristic climate of high latitudes in the polar regions. It is characterized by intense cold due to low solar radiation. Due to the large inclination at which the sun’s rays arrive, temperatures are below -50ºC during most of the year. Strong winds and rain are frequent.
  • **Continental:** Comprises a strip that extends south of the Arctic. Summers are rainy, and winters are cold, with average winter temperatures below -10ºC.
  • **Oceanic:** Characterized by abundant rainfall. Despite being a cold climate, extreme temperatures are avoided due to the moderating influence of the sea.
  • **Mountain:** The mountain climate is very special because it depends heavily on altitude. The higher the altitude, the lower the temperature and pressure, and the higher the rainfall, although this varies according to the layout of the landscape, the time of year, remoteness or proximity to the sea, etc.

Desert Climates

Desert climates are characterized by extreme aridity due to scarce rainfall and high evaporation. There are great differences in temperature between day and night. The arid desert climate can be divided into two subtypes:

  • **Warm Desert:** The air is extremely dry, temperatures are high, and rainfall is weak and infrequent. The temperature differences between day and night are significant. There are also marked differences in temperature between summer and winter.
  • **Cold Desert:** Located in regions where the westerly winds arrive after a long journey in mid-latitudes. Produced by the action of mountain barriers, which force the winds to discharge most of their water on the mountains. Dry air masses continue their shift to the east. The temperature difference between day and night is significant.

Biosphere and Biodiversity

  • The **biosphere** includes all living beings on the planet. It encompasses a thin layer (10 km) with irregular limits extending from the bottom of the atmosphere to the higher levels of the crust, extending a few meters into this, to the bottom of the oceans.
  • **Biodiversity or biological diversity** includes the variety of ecosystems, species, and genes that exist in the world, and the variety within and between them. It is the variety of life in all its forms, levels, and combinations.

Levels of Biodiversity

The organization of the components of biodiversity can be expressed in three levels:

  • **Species Diversity:** Refers to the number of different species coexisting in a given area.
  • **Ecological Diversity:** Refers to the variety of ecosystems. The diversity of ecosystems can be studied from the viewpoint of ecoregions, biomes, biogeographic regions, and life zones.
  • **Genetic Diversity:** Relates to the variety of genes that constitute a population. Each species is the reservoir of an immense amount of genetic information.

Biomes

“**Biomes** are large ecosystems characterized by a specific type of flora, fauna, and climate.”