Please enable JavaScript.
Coggle requires JavaScript to display documents.
Geologic Processes Shape the Earth (Volcanoes (Shield volcanoes: Broad,…
Geologic Processes Shape the Earth
Layers of the Earth
From surface to center: crust, mantle, outer core, inner core
Crust - brittle, thin layer
Oceanic crust - youngest, thinnest and densest crust; made of basalt (mafic)
Continental - thick, but low density; made of granite (felsic)
Mantle - largest layer of Earth
Lithosphere - crust and upper mantle
Divided into plates that move across the surface
Asthenosphere - Below lithosphere. Contains convection currents of magma
Outer core - Liquid iron and nickel.
Convection within liquid metal creates Earth's magnetic field
Inner core - Solid iron and nickel. Solid due to pressure
Pressure and temperature increase as you move down towards core
Continental drift theory
Proposed by Alfred Wegner
States that all continents were once connected in a supercontinent called Pangaea, but drifted apart and are currently moving across surface
Evidence
Continents look like they are puzzle pieces
Matching rock layers on currently separated continents
Matching fossils on currently separated continents
Coal that needed a topical climate in Antarctica
Glacier deposits on continents are currently too warm for glaciers
Plate tectonics theory
Proposed by John Wilson
States continents and oceans are on plates that move across surface driven by convection currents in mantle
Hot magma rises up at divergent plate boundaries. Cooling magma drags plate with it as it sinks back down to be recycled at oceanic convergent plate boundaries (trenches)
Evidence
All the evidence that supports continental drift theory
The age of rocks age moving away from diverging plate boundaries
Types of plates
Divergent plates - plates move apart
Features: Mid-ocean ridges, rift valleys, fissure volcanoes
Convergent plates - plates move towards each other
Oceanic-oceanic: Oldest oceanic plate is the densest so it sinks below younger plate
Features: volcanic island arcs and sea trenches
Continental-oceanic: Oceanic plate is the densest so it sinks below continental plate
Features: volcanic mountain ranges and sea trenches
Continental-continental: plates have same density so neither sinks down, both go up
Features: Mountain ranges
Mountains
Folded mountains - Continental plates move together
Syncline - part of fold that curves down
Anticline - part of fold that curves up
Example: Appalachian Mountains
Faulted mountains - Continental plates move apart
Example: Sierra Nevada Mountains
Dome mountain - created by rising magma
Example: Mount St. Helens
Volcanoes
Lava - molten rock. Types include aa, pahoehoe, and pillow lavas
Pyroclasts - solid fragments ejected from volcano
Volcanic gases - include water vapor, carbon dioxide, sulfur dioxide, hydrogen, carbon monoxide, hydrogen sulfide, hydrogen chloride, and hydrogen fluoride
Helped make up our early atmosphere
Shield volcanoes: Broad, low volcano
Second most common type
Has mafic (basalt) lava
Non-violent eruptions
Located along divergent boundaries and hotspots
Cinder cone volcanoes: Made of tephra; very steep
Has felsic (granite) lava
Can have violent eruptions
Can be located at all types of boundaries
Composite volcanoes: Made of alternating layers of lava and pyroclasts; intermediate steepness
Most common type
Has intermediate lava
Occasional violent eruptions
Located along subduction (convergent) zones
Ring of Fire - areas of plate boundaries around Pacific Ocean where earthquakes and volcanoes are common
Hot spots - areas where magma rises up through weak area of the crust.
Are located away from plate boundaries
Earthquakes
Occur at all boundaries
Forces that cause earthquakes
Tension - forces pull apart
Compression - forces push together
Shearing - forces slide pass each other
Faults - Break in the rock layer
Parts
Headwall - Top section of a fault
Footwall - Bottom section of a fault
Types
Normal - part of rock layer falls down; caused by tension
Reverse - part of rock layer pushed up; caused by compression
Strike slip - rock layers slide pass each other; caused by shearing
Epicenter - point on surface directly above the focus
Strength of seismic waves strongest at the surface here. They weaken as they move away
Focus - Point underground where the earthquake actually starts
Seismic waves
Types
P-waves: primary body waves
Fastest moving
Push-pull motion
Can move through all layers of Earth
S-waves: secondary body waves
Second fastest
Shaking (shearing) up and down
Stopped by the liquid outer core
Causes a large shadow zone of missing S-waves on the other side of the planet from focus of earthquake
Longitudinal surface waves
Slowest
Move side-to-side (love waves) or in circle (Rayleigh waves)
Cannot travel through mantle
Measuring
Seismograph - tool that measures earthquakes
Seismogram - paper that shows strength of quake
Locating epicenter
Need three readings to cross over at one point; this is location of epicenter
Richter scale - measures magnitude of earthquake
Each magnitude is 10 times more powerful than the magnitude below it
Mercalli scale - measures effects of earthquake
Effects: building collapse, fires, floods, tsunamis, disease spread, famine