Transcript Ch_5
Chapter 5 The Biogeochemical Cycles Botkin & Keller Environmental Science 5e How Chemicals Cycle • Biogeochemical Cycle – The complete path a chemical takes through the four major components – or reservoirs – of Earth’s systems 1. 2. 3. 4. Atmosphere Hydrosphere Lithosphere Biosphere Botkin & Keller Environmental Science 5e Chemical Reactions • Chemical reaction: – The process in which new chemicals are formed from elements and compounds through chemical change Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Basic parts of a biochemical cycle. A & B are storage compartments where chemicals flow from one compartment to the other. Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Biogeochemical Cycles and Life: Limiting Factors • 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 phosphorus nitrogen 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 Botkin & Keller Environmental Science 5e 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 Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Any Questions Botkin & Keller Environmental Science 5e Chapter 5 Part #2 The Biogeochemical Cycles Botkin & Keller Environmental Science 5e 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 Botkin & Keller Environmental Science 5e Water Cycle Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Animation Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers In what type of rock do you generally find fossils? Why is this the case? Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Animation Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Any Questions Botkin & Keller Environmental Science 5e Chapter 5 Part #3 The Biogeochemical Cycles Botkin & Keller Environmental Science 5e 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. Botkin & Keller Environmental Science 5e The Carbon-Silicate Cycle CaSiO3+CO2<=>CaCO3+SiO2 Reversible reaction that is usually shifted in favor of calcium carbonate. Calcium Silicate forms at very high temperatures. Calcium Carbonate forms on the Earth’s surface. Botkin & Keller Environmental Science 5e CO2 is taken from the atmosphere to make CaCO3. Therefore, the carbon-silicate cycle is considered to have a negative feedback loop on global warming. Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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 Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers 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. – NOTE: This is the only cycle that does not have a gaseous phase. Botkin & Keller Environmental Science 5e Botkin & Keller Environmental Science 5e © 2008 John Wiley and Sons Publishers Any Questions? Botkin & Keller Environmental Science 5e