Earth's Four Spheres
The "spheres" of Earth systems.
Source: Institute for Computational Earth System Science.
1. The Biosphere is the area of the Earth in which living organisms are found. This
region extends from the deepest ocean to just a few kilometers into the
atmosphere. The Earth is unique in this aspect as it is the only known planet in the
solar system in which the conditions are just right to have allowed life to form and
evolve.
2. The Hydrosphere includes all solid (ice on the Earth is often referred to as the
Cryosphere), liquid, and gaseous water on the Earth. Earth's surface is composed
of 71% water.
Did you know?
Earth is commonly referred to as the blue planet because of its vast water
resources. However, 97% of Earth's water is found in the oceans and due to salt
content it is not directly useable by humans. Of the 3% left that is freshwater, 77%
is locked up in glaciers and icecaps.
3. The Lithosphere (Geosphere) includes the entire solid surface of the land, 29% of
Earth's surface, as well as the various layers of Earth's interior.
4. The Atmosphere is a gaseous layer surrounding the Earth and it is composed of a
mixture of gasesincluding mostly nitrogen (78%), oxygen (21%), carbon dioxide,
and water vapour (1%). The greenhouse gases (carbon dioxide, methane, and
water vapour) are important as they help to trap the Sun's radiation; without this
radiation, the Earth would be too cold for life to exist.
** The Anthrosphere has recently been created to describe all of the human created
elements (e.g., buildings, roads, cities, etc.) found on the Earth.
How are the spheres connected?
These spheres are closely connected in many ways. For example, many birds (biosphere) fly
through the air (atmosphere), while water (hydrosphere) often flows through the soil
(lithosphere). In fact, the spheres are so closely connected that a change in one sphere often
results in a change in one or more of the other spheres.
Interactions between the spheres and an event.
Interactions may occur between spheres; for example, warm water from the ocean evaporates
until the atmosphere above cannot hold any more moisture. The wind (atmosphere) moves the
moisture (water vapour) over a colder part of the ocean. The atmosphere becomes cold and
the water vapour changes to rain. The rain falls on the ocean and some islands in the area get
heavy rain too.
Spheres may also be affected due to an event, which may occur naturally such as a hurricane,
volcanic eruption, or thunderstorm, or they may be caused by humans such as water pollution
or climate change.
Analysis of Sphere Interactions
When analyzing interactions between spheres and events it is important to explain why or how
the interactions occur. For example “A decrease in vegetation may have resulted in increased
soil erosion because there were fewer roots to hold the soil in place.”
In this lithosphere-biosphere interaction it is not simply stated that loss of vegetation resulted in
more soil erosion. The statement demonstrates an understanding of the science and the
interaction by explaining the reason for the interaction (fewer roots to hold the soil in place).
Notes…
Investigate the Interactions between Spheres through the images at the Exploring
Earth website and record your answers in your jot notes.
Did you know?
The greenhouse effect is critical in providing conditions suitable for life on Earth.
Without it, the Earth's average temperature would be −19°C instead of 14°C.
Conversely, too much CO2 on Venus results in the temperatures exceeding 400°C,
and the thin atmosphere on Mars that lacks greenhouse gases (GHGs) creates an
environment too cold to be suitable for life.
The atmosphere on Earth is only composed of 0.03% carbon dioxide, and levels of
CO2 have increased by 30% since 1700.
The eruption of Mount Pinatubo in 1991 reduced sunlight that reached the Earth's
surface by 10% and caused northern temperatures to drop by an average of 0.6°C.
To learn more about the interactions between spheres complete the interactive
activity Spheres of the Earth.