Earth System
Scientific Method
Hypothesis - a tentative explanation of observations/experiments
Theory - hypothesis that has survived challenges
Law/Model - a theory that has survived many, many, many challenges
Earth's Shape/Structure
Topography - Continents - 0-1 km above sea level; Ocean bottoms - 4-5 km below sea level
Density stratification - Heavy stuff sank to center, light stuff floated to surface.
Core - Fe, Ni. Outer is liquid and Inner is solid.
Crust - Outer 5 to 40 km; Si, Al, Fe, Ca, Mg, NA, K, O
Mantle - Material in the middle. Si, Fe, Mg, O.
Continents, Oceans, & Atmosphere Form
Continents - lightest materials float to the top
Oceans and Atmosphere - water and gases boiled off during differentiation and volcanoes
Earth Systems
Open System - the earth is an open system. We receive heat from the sun. We lose heat from the earth's interior to space. Earth's interior is cooling over time. We gain matter from asteroid impacts. These were common in the Earth's early history and have decreased with time. Some impacts have had caused mass extinctions (e.g., dinosaurs 65 m.y. ago)
Climate System - interchange of mass and energy among atmosphere, biosphere, and hydrosphere. Driven by heat from the sun. Controls climate, weather and erosion
Plate Tectonic System - formation, movement, interactions, and destruction of large rigid plates found at the surface.
Lithosphere - Strong outermost layer (crust and uppermost mantle, about 100 km thick)
Asthenosphere - Weak solid layer below the lithosphere. Mantle material that is weak because it is hot.
Internal Heat Engine (converts heat to mechanical work causing convection of the Earth's interior - moves continents around, builds volcanoes and mountains).
Geodynamo System - Movement in the liquid outer core generates the Earth's magnetic field
Earth History
Formation - 4.56 Billion Years ago
Liquid Water - 3.8 Billion Years ago
Magnetic Field/Life - 3.5 Billion Years ago
Oxygen in Atmosphere - 2.5 Billion Years ago
Animals appear in Cambrian - 600 Million Years ago
Mass extinction of dinosaurs - 65 Million Years ago after a metorite struck Earth