Transcript Chapter 10
Mineral Resources and The Rock Cycle Mineral: naturally occurring, solid, inorganic Material with a crystalline structure and a Definite chemical composition Rock: Mixture of minerals Mineral Resource: a minerals that can extracted and converted into a resource at affordable prices Natural Hazards • • • • Earthquakes Volcanoes Floods Mass Movements Earthquake: stress in earth’s crust can cause solid rock to deform until it suddenly fractures and shifts along the fault producing a fault. – Two types of Earthquakes: • Deep-focus: caused when one plate slides under another plate (subduction), the plate gets jammed and pressure builds up, then with a sudden movement the plate slips under the other causing a very big earthquake. • Shallow focus: caused by plates sliding past one another. When the plates get locked up and then suddenly move the earthquake is created. • Epicenter: point on earth’s surface directly above the: • Focus: point where initial movement takes place. • Magnitude: size of quake measured on a logarithmic scale called the Richter scale. • Tsunami: earthquake generated water wave. • Control of quakes: geologic mapping, examine history records, building codes, ideally learn to predict • Volcanoes: when magma reaches earth’s surface through cracks or fissures 3 Types: – Composite Cone: large, steep sided, explosive, thick granitic magma, associated with convergent plate boundaries, lots of gas and ash. • Examples: Shield Volcano Shield: flat, nonexplosive, lots of liquid basaltic lava, associated with divergent plate boundaries and hot spots Example: Mass Wasting: movement of rock by gravity • • • • slump, creep, rockfalls, landslides, mudflows factors that affect mass wasting: steepness of slope, amount of moisture, roads, building, fire subsidence: land sinks and forms sinkholes. Caused when underground caves collapse. Can also be from removal of excess oil or groundwater Example: Soil composition Soil Horizons: series of layers or zones with a distinct texture and composition Soil profile: a cross-sectional view of horizons in soil O-horizon: top layer, surface litter which is leaves and debris A-horizon: topsoil layer: some inorganic materials and humus which is partially decomposed organic material. • these two top layers have fungi, bacteria, and protists that break down complex organic solids • A thick topsoil layer is good for crop. B-horizon: (subsoil) broken down inorganic rock C-horizon: parent rock Leaching: • water infiltration occurs when precipitation occurs, this rain washes minerals out of the top layers of soil Soil Texture: The relative amounts of clay, silt an sand, soil with equal amounts of each are called loams which are the best types for growing crops – Soil Porosity: a measure of the volume of pore spaces in the soil – Soil Permeability: the rate that water moves through the soil, which is determined by soil porosity – Soil porosity, texture and permeability determine a soils water holding capacity, aeration and workability • Soil Acidity: (pH), influences the uptake of soil nutrients by plants, also acid soil causes the leaching out of nutrients. PH of 5.5 to 8.5 is an acceptable range for most plants