2.  An understanding of cycles is necessary to address biological, geological, atmospheric and hydrological questions about ecosystems and human impacts on them A generalized cycling of a chemical in an ecosystem

4. Geologic Cycle  Soil and rocks have been continuously created, maintained for over 4.6 billion years  Geologic cycle is a group of cycles: Tectonic cycle, Hydrologic cycle, Rock cycle

5.  Earth’s Structure  Core  Inner: solid, high temp and pressure, made of nickel and iron  Outer: liquid, cooler than the inner core, made of nickel & iron  Mantle  Made of iron, oxygen and silicon (Rock called peridotite)  Solid at the bottom (close to outer core) becomes more pliable and plastic near the surface  Upper layer known as the lithosphere  Crust  Thinnest zone (6 miles deep to 35 miles deep)  Mostly made of silicon and oxygen in the form of quartz (SiO 2 )  Two types of crust:  Oceanic – which is dense and made of basalt  Continental – which is less dense and made of granite

6.  Structure of the Earth Mantle Core Crust Low-velocity zone Solid Outer core (liquid) Inner core (solid) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.) Crust Lithosphere Asthenosphere (depth unknown)

7.  Creation and destruction of the lithosphere  Lithosphere – pliable, solid outer layer of Earth’s mantle, about 60 miles thick  Broken into several large plates  Plates are moving slowly, process is known as Plate Tectonics  Plates “float” on dense material (Magma, found in mantle)  Plates moving at a rate of 2 – 15 cm per year  Moving plates change location and size of continents, alter atmosphere and ocean circulation (thus altering the climate)

9. 3 types of plate boundaries:  Divergent – plates move away from one another  New lithosphere & crust is formed in the gap created by the spreading plates  This is occurring in the ocean and is known as seafloor spreading  Occurring in Atlantic Ocean, formed Mid-Atlantic Ridge

10.  Convergent – plates moving towards one another; Can lead to:  Deep trench (ocean plate) next to a mountain (continental plate)  One plate moves under the other, more dense plate goes under  Called a Subduction Zone  Formed Sierra Nevada Mountains, Andes Mountains  Occurring in Pacific Ocean, formed Mariana Trench  Mountain ranges (two continental plates collide)  Plates collide and both are pushed upwards  Called Uplift  Formed Himalayan Mountains

11. Oceanic plate (more dense) pushed under Continental plate

13.  Transform – plates slide passed one another  Can lead to earthquakes and land shifting

14.  Water cycle; Driven by solar energy  Includes evaporation, transpiration, condensation, precipitation

15.  Made up of many processes that produce rocks and soil  Processes that affect rock cycle are weathering, sedimentation & life  Rocks classified as:  Igneous  Formed by cooling and solidification of magma  Majority of Earth’s crust is igneous  Examples: granite, basalt, pumice

16. © 2003 John Wiley and Sons Publishers

17.  Sedimentary  Formed by piling of materials over time  Majority of Earth’s surface is sedimentary  Examples: sandstone, shale, limestone

18.  Metamorphic  Formed by extreme heat and pressure  Examples: Slate, marble, schist, gneiss

19.  Biogeochemical Cycle – complete path a chemical takes through the four components of Earth’s systems  Four system components: Atmosphere, hydrosphere, biosphere and lithosphere  Residence time of chemical varies based on the component  Atmosphere residence time – short  Hydrosphere residence time – intermediate  Biosphere residence time – intermediate  Lithosphere residence time – long

20.  Some chemical elements have a quick cycle, usually have a gaseous phase or are soluble in water  Examples: oxygen, carbon and nitrogen  Each have a gas phase and are present in the atmosphere  Some elements have a long cycle, usually don’t have gaseous phase and/or insoluble in water (not part of hydrologic cycle)  Example: Phosphorous  Tied up in relatively immobile forms and are returned to ecosystem slowly, usually by geological processes

21.  Continuation of biogeochemical cycles critical to maintenance of life on Earth  We have been able to create biogeochemical cycles  Can have positive or negative consequences  Benefits crop production  Negative effects on Lake Washington