THE FOUR SPHERES OF THE EARTH

Everything in Earth’s system is placed into one of the four subsystems: land, water, living things, or air. The subsystems are known as “spheres.” Specifically, they are known as the geosphere (land), hydrosphere (water), biosphere (living things) and atmosphere (air). Environmentalists use this system to classify and study the organic and inorganic materials found on the Earth.

No sphere works on its own. All the spheres in the system interact and overlap. In the section, we shall discuss the various interactions that occur among the spheres:

1. Hydrosphere and Atmosphere

The evaporation that occurs in the hydrosphere forms the medium for cloud and rain formation in the atmosphere. The atmosphere brings back this water to the hydrosphere in the form of rain.

2. Hydrosphere and Geosphere

Hydrosphere provides the necessary moisture required to weather and erode rocks in the geosphere. The geosphere, in turn, allows the ice to melt and the water bodies to flow back into the oceans.

3. Atmosphere and Geosphere

The atmosphere provides the required heat and energy for the breakdown and erosion of rock in the geosphere. The geosphere, in turn, reflects the sun’s energy to the atmosphere.

4. Biosphere and Hydrosphere, Atmosphere and Geosphere

The biosphere receives sunlight and gases from the atmosphere. It collects water from the hydrosphere and a living medium from the geosphere.

All four spheres can often be found in a single location. For example, the soil may contain minerals from the geosphere, moisture within the soil from the hydrosphere, insects and plants from the biosphere inhabiting the soil and pockets of air present between the soil pieces. From this, we can conclude that the complete system is what makes life as we know it.

The Geosphere

The geosphere includes all the elements that form the crust and core of the Earth. Rocks and sand particles ranging from drylands to those found at the bottom of the ocean are examples of the geosphere. Examples also involve minerals, lava, molten magma and mountains. The geosphere undergoes constant processes that modify other spheres. One of the examples is the rock cycle.

THE ROCK CYCLE

The rock cycle is the process that describes the gradual transformation between the three main types of rocks: sedimentary, metamorphic, and igneous. It is occurring continuously in nature through geologic time.

In this cycle, the melted rock from below the Earth’s crust is blown out to the surface through vents as lava. Hardened lava, together with rock materials, is weathered and eroded from earth movements. The eroded particles end up somewhere and build up. After many years of buildup, the pressure from the overlying weight causes them to bury themselves more in-depth in the crust. They are melted by the extreme heat until they are spewed out to the surface again. You may have noticed that this cycle doesn’t conclude on its own. It is affected by other factors such as the wind, temperature and water, which are a part of other spheres.

What Causes the Rock Cycle

It occurs due to:

• Plate tectonic activity

• Weathering

• Erosional processes

Why is the Rock Cycle Important

• Helping in the formation of soil thus sustaining every life forms on earth

• Forming life-sustaining minerals such as sodium, iron, potassium, and calcium into the biosphere. 

The Hydrosphere

The hydrosphere refers collectively to all forms of water on Earth. It includes surface water bodies like rivers, oceans, lakes, and ponds, groundwater, water vapor (clouds and fog) in the atmosphere, and ice.

Hydrosphere clearly distinguishes our planet from others, as almost two-thirds of the Earth is covered with water. However, not all water is available to us. The water below the water table cannot be made available for human use. Further, all available water is not fit for drinking purposes.

How is Water Distributed in the Hydrosphere

97.5% of Earth’s water is seawater and thus salty, leaving only 2.5% fresh water. Within 2.5%, nearly 70% is frozen, and only 30% is underground. The frozen part of the hydrosphere consists of glaciers, ice caps, and icebergs. This part of the hydrosphere is called the cryosphere.

What Makes Up the Hydrosphere

The different components of the hydrosphere vary in their state (solid, liquid, or gas) and the location where they are found. It is composed of the following:

1. Oceans: It is the largest reservoir of water on Earth. The water here is salty.

2. Fresh water: It is less abundant than salt water and is available as:

a) Surface water: The water present in lakes, rivers, and streams

b) Groundwater: The water present beneath the Earth’s surface in rock pores and the fractures of rock formations

3. Glacial water: The water that melts from glaciers

4. Water vapor: The water present in the atmosphere

In addition to water, the hydrosphere also contains dissolved minerals, dissolved gases, and particulates.

All forms of water on Earth are recycled and interchanged from one form to another through the water cycle.

Hydrosphere and the Water Cycle

The water in various forms moves through the hydrosphere in a cycle known as the hydrologic or water cycle. It is powered by the energy of the sun. The movement of water within the hydrosphere and the exchange of water with the cryosphere are the basis of the hydrologic cycle.

The different steps of the cycle are described below: