Earth’s Structure and Surface

I. Formation of the Earth A. Earth formed 4.5 billion years ago from clouds of dust. B. The dust was the remains of a cosmic explosion which is estimated to have occurred about 15 billion years ago.

C. Particles collided forming large rocks which formed the earth and other planets.

II. Separated by Density A. On a young earth, matter was mostly molten, causing more dense objects to sink and less dense objects remain on the surface. B. The less dense material cooled forming a thin crust. C. The atmosphere and oceans eventually began to form. A. On a young earth, matter was mostly molten, causing more dense objects to sink and less dense objects remain on the surface. B. The less dense material cooled forming a thin crust. C. The atmosphere and oceans eventually began to form.

III. Layers A. Earth’s Layers: Crust (5 to 46 miles thick) Mantle (1800miles thick) Upper Mantle Lower Mantle Core Outer Core (3200 mi thick) Inner Core (4000 mi thick)

B. Core 1. Inner core is solid and the outer core is liquid. 2. Comprised of iron alloys and silicates. 1. Inner core is solid and the outer core is liquid. 2. Comprised of iron alloys and silicates.

C. Mantle 1. Layer just outside the core (thickest) 2. Hot, solid rocks that are near their melting point. 3. Comprised of silicates 1. Layer just outside the core (thickest) 2. Hot, solid rocks that are near their melting point. 3. Comprised of silicates 4. Solid rock but flows like a viscous liquid.

D. Crust 1. Outermost layer - thin and rigid floating on mantle. 2. Composed of two types of crusts that differ greatly. 2. Composed of two types of crusts that differ greatly.

3. Two Types of Crusts a. Continental Crust – Forms the continents and shallow seabeds. Mostly consists of granite. a. Continental Shelf - the submerged border of a landmass (continent) where it meets the ocean floor. b. Oceanic crust – Below the ocean. Consists of minerals, called basalt. (Basalt – fine grained rock formed from solidified lava) a. Continental Crust – Forms the continents and shallow seabeds. Mostly consists of granite. a. Continental Shelf - the submerged border of a landmass (continent) where it meets the ocean floor. b. Oceanic crust – Below the ocean. Consists of minerals, called basalt. (Basalt – fine grained rock formed from solidified lava)

4. Comparison of Continental and Oceanic Crusts Continental Oceanic Density: 2.7 g/cm 3 3 g/cm 3 Thickness: 0-30 km 0 to 10 km Age: OldYoung Color: Light Dark Composition: Na, Ca, & Al Fe and Mg Continental Oceanic Density: 2.7 g/cm 3 3 g/cm 3 Thickness: 0-30 km 0 to 10 km Age: OldYoung Color: Light Dark Composition: Na, Ca, & Al Fe and Mg

IV. Origin and Structure of the Ocean Basins A. In 1620, Sir Francis Bacon noted that the coasts of continents fit together like puzzle pieces.

B. Pangaea (225 million yrs ago) 1. Pangaea – early theory that the earth was once a supercontinent consisting of only one landmass connecting all continents together. 2. Alfred Wegener suggested this theory in 1912.

C. Theory of Plate Tectonics 1. Wegener’s theory received very little acceptance at first due to lack of proof. 2. In the 1950/60s scientists concluded that the continents had drifted and resulted in a single plate being divided into multiple plates. 3. plate tectonics is the theory that explains the movement of the earth’s 7 major plates. 1. Wegener’s theory received very little acceptance at first due to lack of proof. 2. In the 1950/60s scientists concluded that the continents had drifted and resulted in a single plate being divided into multiple plates. 3. plate tectonics is the theory that explains the movement of the earth’s 7 major plates.

C. Plate Movement 1. Three types of plate boundaries: 2. A. Convergent Boundary 3. B. Transform Boundary 4. C. Divergent Boundary 1. Three types of plate boundaries: 2. A. Convergent Boundary 3. B. Transform Boundary 4. C. Divergent Boundary

C. Plate Movement Convergent Boundary – Where crust is destroyed as one plate dives under another.

C. Plate Movement Transform Boundary – Where crust is neither produced nor destroyed as two plates move horizontally past each other. San Andreas Fault

C. Plate Movement Divergent Boundary – Where new crust is generated as two plates pull away from each other.

D. Mid-Ocean Ridge 1. Mid-Ocean Ridge is a continuous chain of underwater volcanic mountains that formed from the movement of the earth’s plates.

D. Mid-Ocean Ridge 2. Discovered after World War I through the use of sonar of the ocean’s floor. 3. Encircles the entire earth underwater. 2. Discovered after World War I through the use of sonar of the ocean’s floor. 3. Encircles the entire earth underwater.

V. Earth’s Surface A. More than 70% is covered by water. B. Water distribution: Pacific Oceans = 52% Atlantic Ocean = 25% Indian Ocean = 20% Ice = 2% Lakes, Rivers, Atmosphere = 1% A. More than 70% is covered by water. B. Water distribution: Pacific Oceans = 52% Atlantic Ocean = 25% Indian Ocean = 20% Ice = 2% Lakes, Rivers, Atmosphere = 1%

V. Earth’s Surface C. Average Depth of the oceans = 3800m (approx. 12,000ft or 2.36 miles) *deepest is Mariana Trench = 11035m (approx. 36,000ft or 6.86 miles) D. Average Elevation of land = 840m (approx. 2600ft or 0.5 miles) *highest area is Mt. Everest = 8848m (approx. 29,000ft or 5.5 miles) C. Average Depth of the oceans = 3800m (approx. 12,000ft or 2.36 miles) *deepest is Mariana Trench = 11035m (approx. 36,000ft or 6.86 miles) D. Average Elevation of land = 840m (approx. 2600ft or 0.5 miles) *highest area is Mt. Everest = 8848m (approx. 29,000ft or 5.5 miles)