Presentation on theme: "Exploring the Deep GEO/OC103 Lecture 4: The Structure of the EARTH."— Presentation transcript:
Exploring the Deep GEO/OC103 Lecture 4: The Structure of the EARTH
The Edge of the Sea "Now I hear the sea sounds about me; the night high tide is rising, swirling with a confused rush of waters against the rocks below …. Once this rocky coast beneath me was a plain of sand; then the sea rose and found a new shore line. And again in some shadowy future the surf will have ground these rocks to sand and will have returned the coast to its earlier state. And so in my mind's eye these coastal forms merge and blend in a shifting, kaleidoscopic pattern in which there is no finality, no ultimate and fixed reality - Earth becoming fluid as the sea itself." Rachel Carson, The Edge of the Sea, 1955
How do we know what’s inside the Earth? Direct Observations: Exposures on Surface Up from 50 km (30 miles) depth Drilling To 15 km (10 miles) Volcanic Material Up from 200 km (120 miles) depth
How do we know what’s inside the Earth? Indirect Observations: Magnetic Field Iron core. Gravity Field Densities: –Crust: 2 - 3 gm/cm 3 –Mantle: 3.3 - 5.8 gm/cm 3 –Core: 10.8 gm/cm 3 Earthquake Seismic Waves Physical state of crust, mantle, core.
LITHOSPHERE –rigid outer shell –crust and upper mantle (~ 50 to 200 km thick) –somewhat brittle, breakable –cold (like butter out of fridge) ASTHENOSPHERE –warmer, plastic layer under lithosphere –mantle from ~ 150 to 700 km –squishy, plastic –warm (like softened butter) LOWER MANTLE –Solid, but can flow over time! –~700 to 2900 km OUTER CORE –liquid INNER CORE –solid Interior of Earth by STRENGTH
PLATE TECTONICS Tectonics: From the Greek “tecton” builder “architect” The study of large features on Earth’s surface and the processes that formed them.
Large features: – continents, mountain ranges – ocean basins and processes: – earthquakes – volcanic eruptions due to movement of plates of Earth’s outer shell. All resulting from mantle convection PLATE TECTONICS :