Biogeochemical Cycles - Lecture

• Rock Cycle: 3 rock types are igneous, sedimentary, metamorphic

  • igneous: crystallizes magma or lava

  • sedimentary: lithified sediments

  • metamorphic: metamorphized rocks

• No set route for rocks in rock cycle

• Rocks and landforms are shaped by tectonic activity and surficial processes (water, wind and ice)

  • Water, wind, and ice are responsible for weathering, erosion, transportation and deposition of sediment

• Plate tectonics: responsible for uplift, melting, heat, and pressure

Plate Tectonics

• Earth’s Interior

  • crust: thin, brittle rock

  • asthenosphere: soft, ductile rock

  • mantle: solid, elastic rock

  • outer core: molten iron and nickel

  • inner core: solid iron

• Earth’s surface is broken into plates called lithospheric plates

  • average thickness is 100 km

• Plate tectonics: movement of lithospheric plates

  • evidence: sea floor spreading, deep drilling, paleomagnetism, hot spots

  • produces: ocean basin,

Types of Plate Boundaries

• Convergent: plates collide or subduct, destroys lithosphere

  • ocean-continental: volcano chutes

  • ocean-ocean: volcanic island chains

  • continent-continent: mountains

• Divergent: plates pull apart which creates new lithosphere

  • ocean-ocean: mid ocean ridges

  • continental-continental: rift valleys

• Transform: lithospheric plates move past each other

  • no creation or destruction of lithosphere

  • earthquakes

Everything on this planet is affected by plate tectonics

• create new zones of resources

• volcanoes and earthquakes

• determine properties of rock and soil which we depend on for construction and agriculture

• modifies flow patterns in oceans, influencing climate change

Wind, Water, and Ice

• Modify and create landforms

• Ice

  • glaciers

  • permafrost

    • abrade, pluck, deposit

  • Glaciers: mass of moving ice (snow and

    • two types: continental ice sheets and alplane (mountains)

    • 10% cover land surface

      • Greenland, Alaska, Antarctica, Norway, Canada, Cascades, Rocky Mountains

    • glacial surge: rapid advance of ice - can radically change environment

    • Glacial Deposits: sediments deposited by glaciers

      • sediments: sand, silt, clay, gravel

      • till: unconsolidated, poorly sorted directly deposited by glaciers

      • moraine: hill of till

      • outwash: poorly sorted deposited by glacial meltwater

      • eranatios: boulders of different bedrock (exotic)

  • Glacial Erosion

    • valleys: u-shaped

    • cirques

    • horns

    • fiords

    • lakes

  • Careful evolution of recently glaciated area for planning and building

  • Permafrost: permanently frozen ground

    • special engineering problems are associated with design, construction, and maintenance of roads, railroads, cornfield, pipelines, and buildings in permafrost areas

    • hazards: when melted can lead to unstacked materials, subsidence (sinking at surface), landslides,

• Wind

  • wind blown deposits

    • loess: blown silt

    • sand: dunes

    • sand dunes: constructed under the influence of wind from sand moving close to the ground

      • potential problem: dune —

        • problem with construction of land in railroads and —

    • Loess: windblown silt

      • can travel high and far (1000 m high) - derived from glacial outwash

      • can lead to dust storms: dust bowl of 1830s

      • most found along Mississippi River and PNW

Water Cycle

• summarizes how water, water vapor, ice flow through environment

• powered by sun and gravity

• most water that falls on surface runs off into river structures, lake, ocean

• causes erosion

• transports sediment and nutrients between ecosystems

• components: evaporation, transpiration, condensation, precipitation, infiltration, percolation, runoff, interception

• sources of sinks: oceans, rivers, lakes, groundwater, glaciers

  • dependent on precipitation and evaporation rates

• source: a pool that releases more nutrients than it accepts

• sink: a pool that accepts more nutrients than it releases

Carbon Cycle

• Source: plants, deforestation, burning of fossil fuels

• Sinks: sedimentary rocks, oceans, atmosphere, forests, living organisms

  • shift of carbon from ground to air due to burning fossil fuels and cutting forests and burning vegetation

Nitrogen Cycle

• Specialized bacteria

• Nitrogen gas cannot be used by most organisms (78% of atmosphere)

• Processes involved:

  • nitrogen fixation: bacteria combines: nitrogen and hydrogen

  • nitrification: bacteria covert to nitrate - ammonification used by plants

  • assimilation

  • ammonification

  • denitrification

Phosphorus Cycle

• Most found in rocks and released by weathering (very slow)

Sulfur Cycle

• Sulfur moves between rocks, water, systems

• Source: volcanoes, weathering, (not sulfide, minerals)

• Sink: oceans