Earth Systems

Geologic Time Scale 4 Distinct Eras -used by scientists to describe the timing of Earth’s past events. 4 Distinct Eras Precambrian(Earth formation) 2) Paleozoic(fish & reptiles) 3) Mesozoic(dinosaurs) 4) Cenozoic(mammals) -separated by major extinctions.

GEOLOGY Study of Earth’s interior & exterior processes as it relates to minerals and land formations. 3 Main Layers of Earth 1) Core- innermost zone solid inner core of iron metal liquid outer core 2) Mantle- thick, solid but fluid zone outside the core 3) Crust- outermost layer, mostly oxygen & silicates *Lithosphere- land area of Earth consisting of the crust and outer mantle.

Earth’s Layers

Rock Cycle process of rocks changing from one form to another Mineral - naturally occurring, solid element/compound Rock - any solid material that makes up a continuous segment of Earth’s crust. - usually made of 2 or more minerals

Rock Types 1) Igneous - formed from cooled magma 2) Sedimentary - combination of different sediments pressed together 3) Metamorphic - formed by high temp. & pressure under the Earth (Obsidian) (Breccia) (Gneiss)

Plate Tectonics Movement of Earth’s rigid plates Caused by the flow of heat energy underneath. Plate movement creates 3 boundary types: 1) Divergent plate boundary - plates that move apart 2) Convergent plate boundary - plates that push together - create mountains, subduction zones - can cause earthquakes & volcano formation 3) Transform Fault boundary - plates that slide past each other

Plate Boundaries

RING OF FIRE

Earthquake - abrupt movement along a fault

Volcano area where magma reaches the surface releases solid objects, liquid lava, & gases found near plate boundaries.

External Forces 1) Erosion - carrying away of loose sediment & depositing it elsewhere. 2) Weathering - wearing down of rock by: a) mechanical weathering - physical actions b) chemical weathering - oxygen, carbon dioxide, water

Soil Soil Profile mixture of humus, rocks, air, minerals, water, & organisms - formed by: - weathering of rock - deposition of sediments - decomposition of organic matter

Soil Composition - soil has a characteristic color, texture, structure, & mineral content. - Five soil composition types are: 1) Desert- mostly sand & pebbles 2) Grassland- rich humus & clay 3) Rain forest- acidic, light humus, some clay 4) Deciduous forest- humus-mineral mixture 5) Coniferous forest- acidic humus

Soil Types/Textures - texture determines permeability & porosity Types 1) clay- very fine particles 2) silt- fine particles 3) sand- medium size particles 4) gravel- coarse particles 5) loam- mixture of clay, silt, sand, gravel Small particles = low permeability, high porosity Large particles= high permeability, low porosity

Soil Types/Textures

Soil Erosion - movement of topsoil from one place to another Causes: 1) flowing water 2) wind 3) human activities (farming, logging, overgrazing) Results: 1) loss of soil fertility & ability to hold water 2) sediment runoff causing pollution

Desertification - the process that changes a semiarid region into an unproductive desert region. Causes: overgrazing, deforestation, erosion, salinization, surface mining, soil compaction Solutions: 1) Reduce loss of vegetation 2) Plant new vegetation that will reduce erosion

Excessive Irrigation - too much watering leads to: 1) Salinization - salt accumulation due to evaporation of unabsorbed water. - excess salt becomes harmful to crops 2) Waterlogging - saturating the ground causing excess salt to concentrate at the roots Solutions - irrigate crops more efficiently - plant salt tolerant crops

Soil Conservation Methods for reducing erosion: 1) Conservation-tillage farming - farming with less soil tillage - conventional-tillage leaves soil bare and vulnerable to erosion. 2) Terracing - cutting level layers into a slope for farming 3) Contour Farming - plowing a field across the contour of a slope

4) Strip cropping - varying the type of crop planted from row to row 5) Alley cropping - planting crops between rows of trees/shrubs 6) Wind breaks - planting trees along the edge of fields