Ch.4, Sec.1 – Inside the Earth - the Earth is divided into three basic layers: the crust, the mantle & the core - the densest layer is the __________ due to the immense amount of gravitational pull & types of radioactive elements The Crust The Crust  crust: the thin and solid outermost layer of the Earth above the mantle - the thinnest layer of the Earth with a width of 3 to 63 miles & labeled as continental or oceanic - mostly made from silicon, oxygen & aluminum

Ch.4, Sec.1 – Inside the Earth The Mantle The Mantle  mantle: the layer of rock between the Earth’s crust and core (1,800 miles wide) - contains most of Earth’s mass (67%) & is denser than the crust The Core The Core  core: the central part of the Earth below the mantle (2,130 miles wide) - contains 33% of Earth’s mass & is mostly made of iron and nickel

Ch.4, Sec.1 – Inside the Earth The Physical Structure of the Earth The Physical Structure of the Earth - the Earth is divided into 5 physical layers based on physical properties (see pgs. 98 – 99):  1. lithosphere: the solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle we call tectonic plates (1,800˚F)  2. asthenosphere: the plastic layer of the mantle on which the tectonic plates move (1,800˚F)  3. mesosphere: the strong, lower part of the mantle between the asthenosphere & the outer core (1,800˚F)

Ch.4, Sec.1 – Inside the Earth  4. outer core: the liquid layer of the Earth below the mantle (6,700˚F)  5. inner core: the solid, dense center of the Earth, which is 4,000 miles beneath the surface (7,800˚F)

The Rock Cycle (pgs.30-31)

Ch.4, Sec.1 – Inside the Earth Tectonic Plates Tectonic Plates  tectonic plate: a block of lithosphere that consists of the crust and the rigid, outermost part of the mantle - the Pacific plate is the largest & has created a large ring of volcanoes around the Pacific Ocean called the “Ring of Fire”

Ch.4, Sec.1 – Inside the Earth The Ring of Fire The Ring of Fire

Ch.4, Sec.1 – Inside the Earth - tectonic plates completely cover the surface of the asthenosphere - plates are normally thicker where continents are & thinner under the oceans Mapping the Earth’s Interior Mapping the Earth’s Interior - seismic waves from earthquakes travel through the Earth at different speeds (slower through a liquid & faster through a solid) - seismographs measure the times at which different seismic waves travel through the Earth’s interior

Ch.4, Sec.1 – Inside the Earth

1. Why do seismic waves travel faster through solids? ___________________________________________________ 2. Why do seismic waves travel slower through liquids? ___________________________________________________ 3. Where is the greatest amount of volcanic & earthquake activity? ___________________________________________ 4. Is the crust more dense under the oceans or the continents? Why? ______________________________________________ 5. What two factors cause metamorphic rocks to form? ___________________________________________________