Part 1
What is a Lithosphere?
The surface layer of the Earth
Also called the Lithosphere
S-Waves
Secondary/Shear waves.
Arrives second.
Moves through the ground like a snake.
Can ONLY travel through SOLIDS!
Volcanos and thier hazards
Cinder Cone - Erupt rock, ash and cinders.
Shield - Broad gentle slopes, erupt lava.
Composite - Steep slope, explosive eruptions of ash, lava, cinders, pyroclastic cloud.
Hazards: pyroclastic cloud is 1300of moving up to 100 mph, lava flows, toxic gases, and lachars - mud flows of ice, snow, boulders, and debris.
Plate Tectonics
Plate tectonics are the study of the Earth's crustal plate movement (Alfred Wegener).
Ocean and Contionental crust plates, ocean plates are thinner (4mi), basaltic, and more dense, continental plates are thicker (25mi), granitic and less dense, convergence (together), divergence (apart), and transform (different direction).
Convection currents of magma in the asthenosphere, and hot magma rises then spreads out cools and then sinks. Also known as Density Currents.
Evidence of Plate Tectonics
Contionents fit like a puzzle, and matching fossils, rock strata, &mineral deposits.
Types of crust
Oceanic: Basaltic, Mafic, D= about 10km thick
Contionential: Granitic, Felsic, Density= about 30+km thick
L-Waves & Rayleigh Waves
Surface waves that ripple up and down like water waves.
Cause's the most structural damage.
Places where volcanos form
Subductions Zones: Places where ocean crust pushes under ocontionential crust.
Hot Spot: Place where mantle plumes melt through the crust, creates a line of volcanos as the crustal plate moves away form the hot spot, and some examles are The Yellowstone Hot Spot, and the Hawaiian Hot Spot.
Rift Zone: Divergent zone where crust moves apart erupting lava.
Types of plate boundries.
Divergent: Plates move apart, happens along mid-ocean ridges and rift zones, new crust (basalt) is found at the ridge.
Convergent: Plates move together (collide). Subduction Zones.
Seafloor Age matching
From A->B age decreases to the mid-ocean ridge then increases.
What are Earthquakes?
Energy waves released by the crust
Caused by shifting faults
Waves go out in all directions
Seismograph & Seismogram
Seismograph: Insturment that detects Earthquakes.
Seismogram: Recording made by a Sismograph.
Types of Convergent boundries
Continent vs. Continent: Form mountain ranges (Himalayan mountains).
Ocean vs. Continent: Form volcanic mountain ranges (Cascade Mountains, Andes Mts.).
Ocean vs. Ocean:Form volcanic island arcs (Krakatoa in Indonesia).
Magnetic Reversals
Areas of reversed magnetism correlate (match) with bed rock age.
Faults, Focus, and the Epicenter
Faults: Fracture zones where the crustal plate moves.
Focus: Actual starting point of the Earthquake.
Epicenter: Position on the surface above the focus.
What can we do with Seismograms?
Finding the epicenter distance, P and S-wave travel times, P and S-wave arrival times, and locating epicenters on a graph.
Transform plate boundries
When plates slide past eachother (left to right or vise versa).
P-Waves
Primary waves are the fastest type of seismic wave.
Arrive 1st
Compressional
Travels through all matterials (solids, liquids, and gases)
Locating the epicenter and Shadow Zones.
Locating the epicenter: Find the epicenter distance from 3 seismic stations, draw a circle around each location, the epicenter is located where all 3 cirlces intersect (Triangulation).
Shadow Zones: Zones where NO seismic waves are recived, and they cause by refractions.