1.2: Earth Systems Overview

The Earth system is made up of four fundamental subsystems, or spheres. These are referred to as spheres due to the spherical shape of planet Earth, which results in a spherical distribution of the subsystem. The four major spheres are the atmosphere, hydrosphere, biosphere, and lithosphere/geosphere. In the diagram below and to the left, these are abbreviated. In a moment, we will explore an expanded view of these spheres that includes three additional subsystems.

Figure \(\PageIndex{1}\): Earth system interactions due to an “Event”. Events can be a wide variety of things that trigger interactions, or forcings, within the Earth system. (Wheeling Jesuit University/NASA Classrooms of the Future; reproduced with permission.)

Events effect the Earth system as a whole, though they usually begin within a particular sphere. Let us explore a volcanic eruption as an example. When a volcanic eruption occurs, what happens?

• Ash and rock are blasted into the atmosphere;
• Gases are emitted into the atmosphere;
• Lava may run downslope;
• Pyroclastic flows, superheated ash, may rush downslope at great velocity;
• Lahars, or mudflows, may result from the rapid melting of snow and ice, bringing large amounts of debris downslope;
• Flora and fauna in the immediate vicinity of the volcano may be killed.

There are other effects associated with volcanic eruptions. If you were to place the eruption in the very center of this diagram and write some of these interactions along the golden arrows toward a sphere, where would you place them? These are direct effects on each sphere from the event.

These direct effects are not the end of the story. You can see that arrows also connect each sphere to every other sphere. What are some of the indirect interactions (forcings) that result from the eruption? For example, how is the biosphere affected by alterations in the lithosphere? Ultimately, understanding the interconnectedness of the Earth system is critical for gaining a holistic view of how our planet is affected by individual events. In the history of our planet, there are no shortage of such events!

Earth System Forcing Events

Types of forcing events and their effects on the lithosphere/geosphere, hydrosphere, atmosphere, and biosphere.

Forcing Event	Lithosphere/Geosphere	Hydrosphere	Atmosphere	Biosphere
Melting of Polar Ice	Direct - Isostatic adjustment as ice located on land melts	Direct - influx of freshwater into the marine realm affects thermohaline circulation. Change in planetary albedo leading to warmer seawater due to the loss of light-colored ice	Direct - Loss of sea ice leads to warming of oceans and changes in evaporation and weather patterns	Habitat fragmentation of organism ranges in polar regions
Stratovolcanic Eruption	Direct - Release of eruptive materials in the vicinity of the mountain and the creation of volcanic strata	Indirect via Atmosphere - influx of sulfur and carbon dioxide may lead to lower water pH	Direct - influx of ash, sulfur and carbon dioxide	Direct - Major effects on life in the vicinity of the volcano; Temporary regional or even global cooling affects some groups of organisms
Supervolcano Eruption	Direct - Major new volcanic deposits form over a large area. Vicinity of eruption subject to collapse.	Indirect via Atmosphere - surge of carbon and sulfur dioxide in atmosphere leads to lower pH in marine and freshwater environments.	Direct - Major influxes of volcanic gases and ash for extended periods of time.	Direct - Local, regional, and perhaps global extinctions due to deposits of massive amounts of volcanic material and extended global cooling
Deforestation	Indirect via Biosphere - Loss of vegetation leads to more mass wasting events	Indirect via Biosphere - Loss of vegetation affects regional transpiration, water storage, and drainage patterns	Direct - Loss of plant life leads to higher concentrations of carbon dioxide in the atmosphere	Direct - Habitat fragmentation and biodiversity loss. Possible localized or regional extinctions
Asteroid Impact	Direct - Major crater formed, ejecta deposits created over large area; high-pressure metamorphism in zone of impact; Seismic energy release	Direct - Vaporization of large amounts of surface and groundwater from a local to global level, depending upon size and composition of impactor	Direct - Frictional heating as impactor enters atmosphere; Heating as hot ejecta is thrown into atmosphere and exosphere that rains back down on Earth; Introduction of impact related particulate matter	Direct - local to global extinction event
Earthquake	Direct - Local to regional changes in landscape near fault	Indirect via Geosphere - Possible tsunamis or coastal landslides and turbidity currents	Indirect via Geosphere - Release of dust, debris, and toxic gases in some instances	Direct and Indirect - Depending on the species, building collapse and liquefaction can lead to death; Ecosystem changes are possible
Burning of Fossil Fuels	Indirect via Atmosphere - Addition of particulate matter and black carbon to sedimentary deposits; Climate change leads to other downstream effects	Direct - Changes in regional evaporation rates due to warming; Changes in hydrologic cycle	Direct - addition of carbon dioxide warms the troposphere; Changes in weather patterns	Direct - Climate warming leads to biodiversity loss, extinction, etc.
Viral Pandemic Among Human Population	Indirect - Social isolation and pause in economic activity leads to lower ambient seismic activity	Indirect - Reduction in pollution; Reduction in habitat disturbance from recreational boating	Indirect - Reduction in air pollution due to changes in economic activity and energy production	Direct - Widespread sickness and mortality among human species

This table lists a few examples of forcing events in the Earth system and some of their direct influences on one or more spheres. Some forcing events may not directly influence every sphere, rather only have an indirect secondary effect.

Earth Systems Interactions - Quiz

"Globe" by andrewasmith is licensed under CC BY-SA 2.0.

Exercise \(\PageIndex{1}\)

A volcanic eruption emits sulfur dioxide gas.

a. Between event and hydrosphere

b. Between event and atmosphere

c. Between event and biosphere

d. Between event and lithosphere/geosphere

Answer

b. Between event and atmosphere

Exercise \(\PageIndex{2}\)

A volcanic eruption creates pyroclastic flows of super-heated gas and ash that rush downslope.

a. Between event and atmosphere

b. Between event and hydrosphere

c. Between event and lithosphere/geosphere

d. Between event and biosphere

Answer

d. Between event and biosphere

Exercise \(\PageIndex{3}\)

When volcanoes erupt, rapid melting of snow and ice can lead to lahars, or mudflows.

a. Event to Atmosphere

b. Event to Biosphere

c. Event to Hydrosphere

d. Event to Lithosphere/Geosphere

Answer

c. Event to Hydrosphere

Exercise \(\PageIndex{4}\)

Pyroclastic flows from a volcanic eruption event, in this case Mt. St. Helens in 1980, can have a downstream effect connecting the lithosphere/geosphere to...

a. Hydrosphere

b. Atmosphere

c. Biosphere

Answer

c. Biosphere