Prelude: What is Geology? Nature of the scientific method - Class discussion Overview of Earth Systems Origin of the Earth and Solar System Nebular hypothesis Today: Lecture Today: Lecture Overview Overview
Prelude: What is Geology?
Nature of the scientific method
- Class discussion
Overview of Earth Systems
Origin of the Earth and Solar System
Nebular hypothesis
Today: Lecture OverviewToday: Lecture OverviewToday: Lecture OverviewToday: Lecture Overview
http://http://geologygeology.asu.edu/jfarmer/g_stu_1.html.asu.edu/jfarmer/g_stu_1.html
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Solid EarthSolid Earth Interior of the Earth is losing heat.Primary source of heat: Radioactive decayHeat loss drives convection, based on density differences
Hotter stuff is lighter and risesCooler stuff is denser and sinks.
Prelude:Prelude: Earth’s internal structure
crust
mantle
core
Oceanic 0-6 km (“young”, < 180 m.y.)Continental 0-34 km (older, up to 3.8 b.y.)
Upper 34-670 kmLower 670-2900 km
Outer (liquid) 2900-5160 kmInner (solid) 5160-6370 km
3 distinct divisions:
Earth’s dynamic interior and crust
Heat loss drives plate tectonics
Three types of plate boundaries
Prelude: Plate TectonicsPrelude: Plate TectonicsPrelude: Plate TectonicsPrelude: Plate Tectonics
AtmosphereAtmosphere
Protection from Sun’s heat & UV rays
Weather: due to exchange of energy between Earth’s surface & atmosph. between atmosph. & outer space
Strongly interacts w/ surface
Blanket of gases surrounding the EarthBlanket of gases surrounding the Earth
HydrosphereHydrosphere
Oceans (most prominent) 71% of surface of Earth
Streams, lakes, glaciers, underground water
Atmosphere
Water portion of EarthWater portion of Earth
CryosphereCryosphere
Glaciers
Permafrost and ground ice
Polar ice caps
Frozen polar seas
Icy portion of Earth’s crustIcy portion of Earth’s crust
BiosphereBiosphere
Earth’s biosphere occupies both the surface and subsurface to depths of a few kilometers
Life occupies an extreme range of environments
Life strongly interacts with the atmosphere, the hydrosphere and the solid earth to affect their composition and long-term evolution (these interactions are called ecology!)
Earth’s EcosystemsEarth’s Ecosystems
Fungi and PlantsPlants consume carbon dioxide and produce oxygen via photosynthesis. Most of the 21% oxygen in our atmosphere derives from this process!Fungi and and plants form symbioses called Lichens and Mycorrhizae that alter rocks and produce soils.
LichensMycorrhizae
Credit: Sharnoff
Credit: INVAM
Against a constant backdrop of gravity, the atmosphere, hydrosphere and
biosphere interact with the rocks of the Earth’s crust to break them down and transport them to depositional basins
(e.g. the oceans) as sediment. The cycle is renewed as internal processes of plate
tectonics create new crust and uplift it to form mountain ranges.
Earth FormationEarth Formation
Planets thought to have formed:
At same time
From same material as the Sun
Nebular hypothesis
Solar system formed from giant cloud of mostly hydrogen and helium, and a small percentage of heavier elements.
Nebular Hypothesis:
States that the planets of our Solar System were
formed by the “accretion” of materials from a cloud
of gas and dust called a solar “nebula”.
Collapse of the nebula under its own gravity formed a
rotating disk around a dense, central core of
material. This core eventually became hot enough to form the Sun.