(1) Introduction Flashcards
What is Geology
The scientific study of the earth
4 spheres that make up Earth
Geosphere (solid earth), Atmosphere (gaseous), Hydrosphere (water in all 3 forms), Biosphere (life-forms).
The interaction between the spheres is continuing since Earth formed.
Physical Geology
- Major branch of Geology which deals with:
- Materials that make up the Earth
- Changes in the surface and interior of Earth
- Forces that cause those changes
“The Dynamic Earth”
- The earth is constantly changing.
- Geologic changes occur in an instant (volcano, earthquake), or over millions/billions of years.
Species come and species go. The only constant for life on earth is change.
Why study Geology
- Direct applications to soils, engineering, chem, physics, and bio.
- Potential career as geologists.
- Natural phenomena are interesting.
- Knowledge about natural geologic hazards.
- Protecting our environment.
- Context of ourselves as humans in relation to planet earth.
Geological materials supply things human society needs.
Geologic Resources: Energy Resources & Mineral Resources
Materials of geologic origin that we extract from the earth for our use. ER: petroleum, coal, uranium, geothermal energy, plastics (derived from petroleum). MR: metals (aluminum) and non-metals (salt)
Base Metals vs Precious Metals
BM: iron, copper, aluminum, lead, nickel, zinc
PM: gold, silver, platinum
Earth’s Interior
Three major concentric zones: Crust, Mantle, and Core
Crust
- Outer layer of rock that forms a thin skin on the earth.
- Relatively rigid.
- 2 types: Oceanic: avg 7 km thick, dense; Continental: 10-70 km thick, avg 30-50 km, thickest under mountains, less dense.
Why oceanic crust denser than continental crust?
- Oceanic crust is made of rock that have denser material
- Oceanic crusts higher in Mg and Fe lower in Si, Na, and K
- Nothing to do with water in top
Mantle
- Middle zone of the earth.
- 2900km thick.
- Inaccessible to direct observation (studied mainly through geophysical methods).
- Solid rock (but high in T and P = plastic behavior)
- BUT parts flow slowly
Core
- Innermost zone of earth
- 3470km thick
- Consists of inner (solid) and outer (liquid) zones
- Inaccessible to direct observation
- Probably consists mainly of iron and nickel (b/c of magnetic field (Ni), density of the earth, and space materials)
Earth is layered with respect to…
- Earth is layered with respect to both compositon and density.
- The volatiles that make up Earth’s hydrosphere and atmosphere came from volcanic degassing during differentiation.
Earth’s two heat engines
External (sun) and Internal (core)
External heat engine
- Circulates atmosphere and oceans
- Influences surficial (on earth’s surface) process (ex: weathering and erosion)
- Destructional process (breaks down land masses)
Internal heat engine
- Heat moving from hot interior to cooler earth
- Convection cells
- Generates tectonic forces within earth that: cause rock to deform; and cause parts of the crust to move horizontally and vertically
- Constructional process (build up land masses)
Earth gets hotter towards…
Earth gets hotter towards its centre
Pressure increases…
Pressure increases with depth of burial under rock.
Where does earth’s internal heat come from?
- Leftover heat from the planet’s formation (vast accumulative of heat during accretion of the planet)
- Radioactive decay (disintegration of natural radioactive elements)
Geologists also subdivide the upper parts of the earth
Lithosphere
- Crust and uppermost mantle
- Avg 70km thick beneath oceans
- ‘litho’ - Greek word for ‘rock’
- Relatively rigid, brittle, and strong
Asthenosphere
- Upper part of the mantle under the lithosphere
- 70 - 200km deep
- ‘asthenos’ - Greek word for ‘weak’
- Soft, flows, plastic
- Lubricates layer over which lithosphere moves
Why is the core suspected to be Iron and Nickel?
Asteroids are made of iron and nickel and earth was produced in space from space materials
