Earth Systems

Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts; Charlene Estrada

Earth Systems

Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts and Charlene Estrada

Throughout its entire 4.54 Ga history, every event in the history of our planet happened because something forced it to happen. As we’ve reviewed in the previous section, an asteroid caused the extinction of the dinosaurs at the end of the Cretaceous period. Extinctions led to new evolutionary pathways for the origination of species. Plate tectonics caused continents to move around. In each of these realities, we might be tempted to simply describe them as they have been here, in a linear fashion. A caused B. We could leave it at that. However, is it that simple?

Within the Earth system, there are subsystems. These subsystems encompass the space environment (exosphere), gaseous environment (atmosphere), liquid environment (hydrosphere), solid environment (lithosphere and geosphere, hereafter lithosphere), and living environment (biosphere). In some cases, the icy environment (cryosphere) is broken away from the hydrosphere and the anthroposphere (human environment) from the biosphere for emphasis.

Energy, coming from the Sun on the one hand and the Earth’s interior on the other, powers these systems. As energy flows through these systems, so do nutrients and elements through biogeochemical cycles. Examples of these include the carbon and nitrogen cycles.

An image of Earth surrounded by depictions of air, land, water, and life.

Earth systems science seeks to understand the interconnectedness of our planet’s air, water, land, and life (M. Ruzek 1999).

The Earth system is made up of four fundamental subsystems, or spheres. 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 six of them.

Earth system interactions due to an "Event". Events can be a wide variety of things that trigger interactions, or forcings, within the Earth system. — Earth system interactions due to an “Event”. Events can be a wide variety of things that trigger interactions, or forcings, within the Earth system.
Graphic: Wheeling Jesuit University/NASA Classrooms of the Future; reproduced with permission.

Events affect 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 event 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 near the volcano may be killed.

There are other effects associated with volcanic eruptions beyond these. 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 there are also arrows connecting each sphere. What are some of the indirect interactions (forcings) that result from the eruption? How is the biosphere affected, for example, by how the eruption directly affects the lithosphere (geosphere)? 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 has been no shortage of such events!

The table below shows some of the relationships between these events that cause a relationship to form between the different spheres, called forcing events. They are called forcing events because they cause a shift in energy flow from one system to another.

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 leads 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 – the 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 – a surge of carbon and sulfur dioxide in the atmosphere leads to lower pH in marine and freshwater environments.

Direct – Major influxes of volcanic gases and ash for extended periods.

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 a large area; high-pressure metamorphism in the zone of impact; Seismic energy release

Direct – Vaporization of large amounts of surface and groundwater from a local to a global level, depending upon the size and composition of the 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 a global extinction event

Earthquake

Direct – Local to regional changes in the landscape near the 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 the hydrologic cycle

Direct – addition of carbon dioxide warms the troposphere; Changes weather patterns.

Direct – Climate warming leads to biodiversity loss, extinction, etc.

Viral Pandemic Among Human Population

Indirect – Social isolation and pause in economic activity lead 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 the human species

Consider how the different systems are connected with these event scenarios below:

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Introduction to Historical Geology Copyright © by Callan Bentley, Karen Layou, Russ Kohrs, Shelley Jaye, Matt Affolter, and Brian Ricketts and Charlene Estrada is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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