Population Growth Our Number One Environmental and Resource Problem
Growth Rate and Doubling Time Exponential growth Growth rate, G, measured as a percentage Doubling time, D=70/G
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Sustainability Development that ensures that future generations will have equal access to the resources of our planet
The Evolving Earth, Geologic Time and Minerals
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A view of Earth Earth is a planet that is small and selfcontained Earth s four spheres Hydrosphere Atmosphere Biosphere Solid Earth
Earth as a system Earth is a dynamic planet with many interacting parts or spheres Parts of the Earth system are linked Characterized by processes that Vary on spatial scales from fractions of millimeter to thousands of kilometers Have time scales that range from milliseconds to billions of years
Earth as a system The Earth system is powered by the Sun that drives external processes in the Atmosphere Hydrosphere At Earth s surface
Earth s internal structure Earth s internal layers can be defined by Chemical composition Physical properties Layers defined by composition Crust Mantle Core
Earth s internal structure Four main layers of Earth are based on physical properties and hence mechanical strength Lithosphere Asthenosphere Mesosphere Core
Earth s internal structure
Discovering Earth s composition Two types of crust Continental crust Lighter Granitic rocks Oceanic crust Denser Composed primarily of basalt
Discovering Earth s Mantle Core composition Solid, rocky layer Composed of rocks like peridotite Thought to mainly dense iron and nickel Two parts Outer core - liquid Inner core - solid
Dynamic Earth The theory of plate tectonics Involves understanding the workings of our dynamic planet Began in the early part of the twentieth century with a proposal called continental drift the idea that continents moved about the face of the planet
Dynamic Earth The theory of plate tectonics A theory, called plate tectonics, has now emerged that provides geologists with the first comprehensive model of Earth s internal workings Plate boundaries All major interactions among individual plates occurs along their boundaries
Distribution of magnitude 5 or greater earthquakes, 1980-1990
Dynamic Earth Plate boundaries Divergent boundary two plates move apart, resulting in upwelling of material from the mantle to create new seafloor Convergent boundary two plates move together with subduction of oceanic plates or collision of two continental plates
Dynamic Earth Plate boundaries Transform boundaries - located where plates grind past each other without either generating new lithosphere or consuming old lithosphere Changing boundaries - new plate boundaries are created in response to changes in the forces acting on the lithosphere
Divergent boundaries are located mainly along oceanic ridges
The East African rift a divergent boundary on land
An oceanic-continental convergent plate boundary
An oceanic-oceanic convergent plate boundary
Earthquake foci in the vicinity of the Japan trench
A continental-continental convergent plate boundary
The collision of India and Asia produced the Himalayas
Testing the plate tectonics model Hot spots Caused by rising plumes of mantle material Volcanoes can form over them (Hawaiian Island chain) Most mantle plumes are long-lived structures and at least some originate at great depth, perhaps at the mantle-core boundary
The Hawaiian Islands have formed over a stationary hot spot
The driving mechanism No one driving mechanism accounts for all major facets of plate tectonics Researchers agree that convective flow in the rocky 2,900 kilometer-thick mantle is the basic driving force of plate tectonics Several mechanisms generate forces that contribute to plate motion Slab-pull Ridge-push
The driving mechanism Models of plate-mantle convection Any model describing mantle convection must explain why basalts that erupt along the oceanic ridge Models Layering at 660 kilometers Whole-mantle convection Deep-layer model
Minerals: Building blocks of rocks Definition of a mineral: Naturally occurring Inorganic solid Ordered internal molecular structure Definite chemical composition Definition of a rock: A solid aggregate or mass of minerals
Structure of minerals Minerals consist of an orderly array of atoms chemically bonded to form a particular crystalline structure For ionic compounds, the internal atomic arrangement is primarily determined by the size of ions involved
Composition of minerals Elements Atoms Basic building blocks of minerals Over 100 are known (92 naturally occurring) Smallest particles of matter Retains all the characteristics of an element
The periodic table
Classification of Minerals Nearly 4000 minerals have been identified on Earth Rock-forming minerals Common minerals that make up most of the rocks of Earth s crust Only a few dozen members Composed mainly of the 8 elements that make up over 98% of the continental crust
Classification of Minerals Silicates Most important mineral group Comprise most of the rock-forming minerals Very abundant due to large amounts of silicon and oxygen in Earth s crust Basic building block is the siliconoxygen tetrahedron molecule Four oxygen ions surrounding a much smaller silicon ion
The silicate (SiO 4 ) -4 molecule
Silicate structures
Classification of Minerals Important nonsilicate minerals Several major groups exist including Oxides Sulfides Sulfates Native Elements Carbonates Halides Phosphates
Mineral Resources The endowment of useful minerals ultimately available commercially Metals and Nonmetals Mineral resources include Reserves already identified deposits Known deposits that are not yet economically or technologically recoverable
Mineral Resources Ore A useful metallic mineral that can be mined at a profit Must be concentrated above its average crustal abundance Profitability may change because of economic changes
Minerals and the Environment Most minerals are only metastable Reactive to air and water Can contribute significant concentrations to soil and water May have impact on human health
The rock cycle