Weathering – the physical breakdown (disintegration) and chemical alteration (decomposition) of rock at or near Earth’s surface Erosion – the physical removal of material by agents such as water, wind, ice, or gravity Weathering and Erosion Formation of Sedimentary Rocks

insoluable

basalt (Mg,Fe) 2 SiO 4 (Mg,Fe)SiO 3 pyroxine H 4 SiO 4 in solution Mg 2+ in solution Fe (III) hydroxide (insoluble, rust) CaAl 2 Si 2 O 8 Ca-feldspar and NaAlSi 3 O 8 Na-Feldspar Ca +2 in solution Na +1 in solution Al 2 Si 2 O 5 (OH) 4 (insoluble, “clay”)

granite SiO 2 quartz SiO 2 (insoluble, “sand”) CaAl 2 Si 2 O 8 Ca-feldspar; NaAlSi 3 O 8 Na-Feldspar KAlSi 3 O 8 K-Feldspar Ca +2, Na +1, K +1 in solution Al 2 Si 2 O 5 (OH) 4 (insoluble, “clay”) (Ca,Na) 2 (Mg,Fe,Al) 5 (Al,Si) 8 O 22 (OH) 2 amphibole (and also mica) Mg +2, Ca +2, Na +1 in solution Al 2 Si 2 O 5 (OH) 4 (insoluble, “clay”) Fe (III) hydroxide (insoluble, rust)

Climate and Weathering

Hot and wet favors chemical weathering

Cold and snowy favors mechanial weathering

Differential Weathering and Erosion creates topography Slowly weathered and eroded - high (Morningside Heights, Palisades, Ramapo Mountains) Quickly weathered and eroded - low (sediments beneath Hudson River and west of Palisades)

Residual topography Hill formed by differential erosion uplift erosion

Clastic Sediments and Clastic Sedimentary Rocks A. Sediments B. Sedimentary Rocks

Energy and Depositional Environment

Worldwide sediment yield of major drainage basins

Migration of meanders leads to cross-bedding crossbed from fieldtrip

Cross-section of Delta note that delta grows (progrades) towards sea

Hjulstrom Curve

Pebbles and cobbles Pebbles and cobbles: hard to get moving, an hard to keep moving

Hjulstrom Curve Sand Sand: easy to get moving, a fairly easy to keep moving

Hjulstrom Curve Silt and Clay Silt and Clay: hard to get moving, but very easy to keep moving

Ocean Sediments Part 1

Evapotite: common during with continental rifting

Fossil Fuels Solid Earth System

petroleum Organic-rich source rock, e.g. shale Maturation through burial at the right temperature Collection in a porous reservoir rock Concentration in trap through buoyancy

Formation of Ores

Some unusual process must: 1) remove specific elements, compounds or minerals from ordinary rock, 2) transport these elements, compounds, or minerals 3) concentrate the elements, compounds, or minerals preferentially at one spot or zone where the transport stops.

the primary mechanisms for concentrating minerals into ores involves either: sorting by density sorting by solubility.

Concentration through liquid immiscibility Low T Desirable element preferentially concentrated into low-volume melt High T

Aqueous fluids in magma As magma cools, the volatiles (mostly water and carbon dioxide) that they contain can form super-critical fluids. supercritical fluids are on the verge of making the phase transition from liquid to gas. because of their extremely high temperature, many elements are soluble. These fluids can concentrate copper, molybdenum, gold, tin, tungsten and lead. The fluids from a large pluton can invade surrounding rocks, along cracks called hydrothermal veins).

Aqueous fluids from granitic magma have invaded surrounding rock porphery copper ore

Mechanisms that involve oxidation state of the water Ground water can carry dissolved materials. These can precipitate out of solution if the water becomes more or less oxidizing.

Example: uranium ore soluable U 6+ is produced during the weathering of igneous rocks. U 6+ was transported by groundwater until it encounters reducing conditions. It is reduced to U 4+ and precipitates as uranium oxide.

Mineral Commodities Solid Earth System

Geothermal Power

6.5 km – expensive but routine, areas of western US are hot

Solution to low permeabiliy Artificially increase permeability by creating fractures “Hydrofracture” … pressurize well until you crack the surrounding rock, routinely used in oil extraction, at least for small volumes of rock

Fresh Water Possibly the most Limiting Resource

US Water Usage, billion gallons / day Irrigation Domestic Supply Public Supply Livestock & Aquaculture Industrial Mining Thermoelectric Power Total 262

How much irrigation water does the world need? 2000 calories/day minimum At 3 cal/liter 670 liters/day  6 billion people  365 days/year = 1.46  liters/year = cubic kilometers per year About 46,000 cu km available

Global impoundments of water 8400 km 3 Not much growth in last decade, except in Asia- Australia

Good luck with the final best wishes for 2009