In addition to the lessons I presented on Earth’s interior and surface topography described last week, I also taught a short lesson on Geospheres and our Earth System. To those who had explored ecology with us in the spring, this was a bit of review though the material was presented in a different manner.
What is a System?
A system is generally described as a set of components that interact within a boundary. A clock is a good example of a system. Mechanical and often electrical components work together to display the time. In recent years, scientists have started to consider Earth, from the very top of the atmosphere to the core at its center, as a system with four major components or spheres that interact in very complex ways.
The area near the surface of the earth can be divided up into four inter-connected “geo-spheres:” the lithosphere, hydrosphere, biosphere, and atmosphere. Scientists can classify life and material on or near the surface of the earth to be in any of these four spheres. The names of the four spheres are derived from the Greek words for stone (litho), air (atmo), water (hydro), and life (bio).
- The geosphere (sometimes called the lithosphere) includes the solid part of Earth, the interior, and the pedosphere, which is the thin, outermost soil layer.
- The hydrosphere is all of Earth’s bodies of water, including groundwater and Earth’s frozen water (the cryosphere).
- The biosphere is all living things, plants and animals, from microbes to humans.
- The atmosphere is the blanket of gas that surrounds Earth, and includes the precipitation, clouds, and aerosols (tiny suspended particles) that are found in air.
Beginning to perceive Earth as a system can begin with something as simple as when we ﬁrst feel warmth from sunshine or get wet standing in the rain. However, truly understanding Earth as a system requires a quantitative exploration of the connections among all parts of the system: air, water, land, and life.
At any moment in time, all matter and energy on Earth is part of one or more of these spheres, and across time, all of Earth’s matter cycles through two or more of these spheres.
Interconnections and Processes
There are many simple examples of the interconnections between components and elements of the Earth system. I’ve listed a few here:
- The roots of plants (biosphere) draw water and nutrients from the pedosphere, exchange oxygen and carbon dioxide with the atmosphere through the process of photosynthesis, and send water into the atmosphere through the process of transpiration.
- Plants also die and decompose to become part of the pedosphere.
- Water evaporates from rivers (hydrosphere) and the soil (pedosphere) to become part of the atmosphere.
- Oxygen in the atmosphere dissolves in a river (hydrosphere).
- Fish (biosphere) draw dissolved oxygen into their bodies from the hydrosphere.
- The sun warms the pedosphere, which transfers its heat to the atmosphere.
- Warmed air transfers heat to cooler land surfaces.
- Evaporation from a lake (hydrosphere) transfers heat to the atmosphere.
- Rivers and ocean currents redistribute heat energy.
- Precipitation can warm or cool the pedosphere on which it falls.
There are also connections between elements within a component of the earth systems. For example:
- Birds eat plant seeds.
- Flowers attract insects and other pollinators.
- Rivers flow into lakes or oceans.
Because of the interconnectedness, changes in one sphere bring about changes in the others. Sometimes these changes are dramatic, but more frequently these changes are more subtle.
- Droughts (atmosphere) can cause severe changes in the hydrosphere, the biosphere, and the pedosphere.
- Rain changes the soil moisture and the amount of water in lakes and rivers.
- Increased water level in a lake has an impact on the plants and animals that inhabit the shoreline.
- An increase in air temperature decreases the amount of moisture in the pedosphere by increasing the rate of evaporation and the rate at which vegetation loses water (transpiration) to the atmosphere.
Lesson Objective – By studying the flow of energy and matter locally, students will begin to build an understanding of how the four components of the Earth system work together to create and maintain Earth’s unique climate.
Last week, I shared with the class a powerpoint from Earth Labs and then assigned them the task of taking a photograph for this week’s lesson. The photo could be of their backyard, the lake, the river, or a park – it was entirely up to them.
I opened today’s lesson by sharing with them several infographics that illustrated the cycles of water and nutrients between the spheres: the hydrologic cycle (water cycle), the carbon cycle (photosynthesis, respiration, and transpiration), the nitrogen cycle, etc. Most of this was review for the students – but for some it was new material.
I modeled for the class the process of identifying the interconnections and processes evident in the photograph I took (example pictured above). I then asked students to annotate a photograph of their study site.
Lastly, the students created a simplified diagram of their study site to highlight the flow of energy and matter among the four components of the Earth system.
If you are interested in doing this lesson with your students, the printables and handouts are available as a FREE download, Geospheres Foldable.