X Prelude: What is Geology? Nature of the scientific method - Class discussion X Overview of Earth Systems X Origin of the Earth and Solar System Nebular hypothesis Today: Lecture Overview

geology.asu.edu/jfarmer/g_stu_1.html OUR COURSE’S WEBSITE Note: NO “www”!!!

“And just what is Geology?” Prelude:

Solid Earth lInterior of the Earth is losing heat. lPrimary source of heat: Radioactive decay lHeat loss drives convection, based on density differences lHotter stuff is lighter and rises lCooler 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 km Lower km Outer (liquid) km Inner (solid) km 3 distinct divisions:

Earth’s dynamic interior and crust F Heat loss drives plate tectonics F Three types of plate boundaries Prelude: Plate Tectonics

Prelude: Earth Systems F Solid Earth F Atmosphere F Hydrosphere F Cryosphere F Biosphere

Atmosphere l Protection from Sun’s heat & UV rays l Weather: due to exchange of energy between Earth’s surface & atmosph. between atmosph. & outer space l Strongly interacts w/ surface Blanket of gases surrounding the Earth

Hydrosphere l Oceans (most prominent) 71% of surface of Earth l Streams, lakes, glaciers, underground water l Atmosphere Water portion of Earth

Cryosphere l Glaciers l Permafrost and ground ice l Polar ice caps l Frozen polar seas Icy portion of Earth’s crust

Water is the primary agent of crustal weathering

Biosphere l Earth’s biosphere occupies both the surface and subsurface to depths of a few kilometers l Life occupies an extreme range of environments l 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 Ecosystems

Earth: The Living Planet

Most of the biodiversity on our planet is microbial!

The Three Domains of Life

Boiling mudpot, Yellowstone Some extremes of life

Fungi and Plants  Plants 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. Lichens Mycorrhizae 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 Earth is one of nine planets comprising the Solar System How did the Solar System form?

Earth Formation Planets thought to have formed: t At same time t From same material as the Sun Nebular hypothesis t 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.