The Greenhouse Effect on Earth Earth’s atmosphere is slightly warmer than what it should be due to direct solar heating because of a mild case of greenhouse effect… The majority of Earth’s atmosphere (N 2 and O 2 ) are not good greenhouse gas. The small amount of greenhouse gases (H 2 O, CO 2 ) traps (absorb and re-emit) the infrared radiation, increasing the temperature of the atmosphere… Click on image to start animation

Target 2.a Analyze how greenhouse gases directly affect global climate change.

Water On Earth The condition is just right! The combination of 2 factors: Distance to the Sun and the greenhouse effect, make it possible for water to stay on Earth. N 2 and O 2 are not greenhouse gas. Not much CO 2 in the atmosphere. Variable amount of H 2 O in the atmosphere…regulated by the temperature.

Greenhouse Gases The primary components of Earth’s atmosphere, N 2 and O 2,do not have a significant role in setting the surface temperature of the planet… Greenhouse gas are efficient in absorbing infrared light… The most important greenhouse gases are: –H 2 O – Water vapor. –CO 2 – Carbon Dioxide –CH 4 – methane

Global Warming T here is a gradual increase in the average temperature of the Earth’s atmosphere in the last 100 years…It has risen about 1°C since 1900… Are human activities causing global warming? What other (non-human) factors can cause global warming? How does global warming affect our life? Just watch the movies…

Earth’s Temperature Variation in the past 1,100 years

Target- 2.d Describe how water’s properties can create weathering and erosion of sediment

Weathering: Two Types Mechanical engineering The breakdown of rock into solid fragments by physical processes Chemical composition of rock NOT altered Chemical weathering The decomposition of rocks and minerals by chemical and biochemical reactions

Characteristics Joints –A fracture of rock, along which no appreciable movement has occurred –Sheet jointing or exfoliation –Frost wedging Abrasion –The gradual wearing down of bedrock by the constant battering of loose particles transported by wind, water or ice The jointing in these rocks has exposed new surface area which has broken and smoothed due to wind, water and ice.

Weathering exfoliation and frost wedging

Frost wedging and biomechanical weathering

Chemical weathering Dissolution –The separation of materials into ions in a solution by a solvent, such as water or acid –Rainwater acts as weak solution of carbonic acid –Anthropogenic actions influence acidity of rainwater The marble grave marker has been attacked by acidic rain because of the calcite composition. The grave marker on the right, while old, has not been dissolved because of its granite composition

Chemical weathering: ion exchange and the chemical breakdown of feldspar

Factors affecting weathering Tectonic setting –Young, rising mountains weather relatively rapidly –Mechanical weathering most common

Factors affecting weathering Rock composition –Minerals weather at different rates Calcite weathers quickly through dissolution Quartz is very resistant to chemical and mechanical weathering Mafic rocks with ferromagnesian minerals weather more easily

Factors affecting weathering Rock structure –Distribution of joints influence rate of weathering Relatively close joints weather faster

Factors affecting weathering Topography –Weathering occurs faster on steeper slopes Rockslides

Factors affecting weathering Vegetation –Contribute to mechanical and chemical weathering –Promotes weathering due to increased water retention –Vegetation removal increases soil loss Vegetation can both hold water And increase weathering. If removed Rocks may also be vulnerable to abrasion

Factors affecting weathering Biologic activity –Presence of bacteria can increase breakdown of rock

Factors affecting weathering Climate –Chemical weathering is more prevalent in warm, wet tropical climates Mechanical weathering less important here –Mechanical weathering is more prevalent in cold, relatively dry regions Chemical weathering occurs slowly here Note: temperate regions such as at the center of the chart undergo both chemical and mechanical weathering, i.e. New York area

Products of Weathering Clay –Tiny mineral particles of any kind that have physical properties like those of the clay minerals –Clays are hydrous alumino-silicate minerals

Products of Weathering Sand –A sediment made of relatively coarse mineral grains Soil –Mixture of minerals with different grain sizes, along with some materials of biologic origin –Humus –Partially decayed organic matter in soil

Erosion and Mass Wasting Erosion is the removal of weathering products from the source and most often occurs by water Erosion –The wearing away of bedrock and transport of loosened particles by a fluid, such as water –Example: Sediment moved along the bottom of a stream

Erosion and Mass Wasting Erosion by wind Particles of sand are transported close to the surface. finer particles of silt and clay can be transported great distances Erosion by ice –Glacier A semi-permanent or perenially frozen body of ice, consisting of recrystallized snow, that moves under the pull of gravity Wind-blown fine sediments such as this dust cloud can Be transported across oceans

Erosion and Mass Wasting Left: deposits of unsorted glacial till from glacier Right: rock polished and striated by glacier

Erosion by ice: glacier removes, breaks and transports rock pieces glaciers scour valleys and deposit piles of debris as moraines

Erosion and Mass Wasting Mass wasting –The downslope movement of regolith and/or bedrock masses due to the pull of gravity Slope failure –Falling, slumping or sliding of relatively coherent masses of rock

Erosion and Mass Wasting: Rock slide, rock fall, and slumping result in downhill transport of broken rock

Erosion and Mass Wasting Flow: If water or air combines with the downward movement, the regolith can “flow” downhill Creep –The imperceptibly slow downslope flow of regolith Unstable slopes move very slowly over long periods of time

Erosion and Mass Wasting

Why do major landslides occur near plate boundaries? Tectonics and mass wasting –World’s major historic landslides clustered near converging lithospheric plates High mountains undergo rapid weathering Earthquakes near plate boundaries can trigger landslides This massive slide was triggered by A magnitude 9 earthquake in Alaska near a subduction zone.

Critical Thinking On Earth, clay minerals are the most common products of weathering. Samples from the Moon do not contain any clay minerals. Why? Why are some granite bodies extensively jointed, while others are essentially joint free?

Critical Thinking On Earth, clay minerals are the most common products of weathering. Samples from the Moon do not contain any clay minerals. Why? Why are some granite bodies extensively jointed, while others are essentially joint free?