chapter 5 · –occurs where one plate slides past another •san andreas fault in california...

Botkin & KellerEnvironmental Science 5e

Chapter 5

The Biogeochemical Cycles


Lake Washington• Large natural lake near Puget sound in

Washington State.• Treated sewage was discharged into

the lake.• Treated sewage, while sterile contains a

lot of Phosphates, many from man made products

• Phosphates are a “limiting factor” for plants, including algae

2


Lake Washington (2)• Addition of Phosphate caused an

“Algal bloom” in a process known as “eutrophication”

• The algae, as it dies and decomposes is stinky

• The algae covering the lake effects the fish by reducing oxygen

• The problem was successfully abated by

3


How Chemicals Cycle• Biogeochemical Cycle

– The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems1. Atmosphere2. Hydrosphere3. Lithosphere4. Biosphere


Chemical Reactions• Chemical reaction:

– The process in which new chemicals are formed from elements and compounds through chemical change


© 2008 John Wiley and Sons Publishers




Biogeochemical Cycles and Life:

• Macronutrients– Elements required in large amounts by all life– Include the “big six” elements that form the fundamental building

blocks of life:carbon oxygen

hydrogen phosphorusnitrogen sulfur

• Micronutrients– Elements required either in

• small amounts by all life or • moderate amounts by some forms of life and not all by others

• Limiting factor– When chemical elements are not available at the right times, in

the right amounts, and in the right concentrations relative to each other


The Geologic Cycle• The Geologic Cycle:

– The processes responsible for formation and change of Earth materials

– Best described as a group of cycles:• Tectonic• Hydrologic• Rock• Biochemical




Tectonic Cycle• Tectonic cycle:

– Involves creation and destruction of the solid outer layer of Earth, the lithosphere

• Plate tectonics:– The slow movement of these large segments

of Earth’s outermost rock shell – Boundaries between plates are geologically

active areas




Tectonic Cycle: Plate Boundaries

• Divergent plate boundary:– Occurs at a spreading ocean ridge, where plates are

moving away from one another– New lithosphere is produced (seafloor spreading)

• Convergent plate boundary– Occurs when plates collide

• Produces linear coastal mountain ranges or continental mountain ranges

• Transform fault boundary– Occurs where one plate slides past another

• San Andreas Fault in California


The Hydrologic Cycle• The Hydrologic Cycle:

– The transfer of water from the oceans to the atmosphere to the land and back to the oceans. Includes:

• Evaporation of water from the oceans• Precipitation on land• Evaporation from land• Runoff from streams, rivers, and sub-surface

groundwater




The Rock Cycle• The rock cycle:

– Numerous processes that produce rocks and soils

– Depends on other cycles:• tectonic cycle for energy • Hydrologic cycle for water

– Rock is classified as • Igneous• Sedimentary• Metamorphic








The Carbon Cycle• Carbon is the element that anchors all

organic substances• The carbon cycle:

– Carbon combines with and is chemically and biologically linked with the cycles of oxygen and hydrogen that form the major compounds of life








The Carbon Cycle:Unanswered Issues

• The Missing Carbon Sink– Substantial amounts of carbon dioxide

released into the atmosphere but apparently not reabsorbed and thus remaining unaccounted for




The Carbon-Silicate Cycle• The carbon-silicate cycle:

– A complex biogeochemical cycle over time scales as long as one-half billion years.

– Includes major geological processes, such as:• Weathering• Transport by ground and surface waters• Erosion• Deposition of crustal rocks

– Believed to provide important negative feedback mechanisms that control the temperature of the atmosphere.




The Nitrogen Cycle• The nitrogen cycle:

– Cycle responsible for moving important nitrogen components through the biosphere and other Earth systems

– Extremely important because nitrogen is required by all living things

• Nitrogen fixation:– The process of converting inorganic, molecular

nitrogen in the atmosphere to ammonia or nitrate• Denitrification:

– The process of releasing fixed nitrogen back to molecular nitrogen




The Phosphorus Cycle• The phosphorus cycle:

– Involves the movement of phosphorus throughout the biosphere and lithosphere

– Important because phosphorus is an essential element for life and often is a limiting nutrient for plant growth.

chapter 5 · –occurs where one plate slides past another •san andreas fault in california...

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