Lec 3: The earth and plate tectonics Flashcards
How many seismic waves are there and how do they travel? (hint:2)
earthquakes generate both compressive waves (P) and shear waves (S).
P wave travels through both solid and liquid.
S wave travels through solid.
Lecture’s goals:
1_ List the layers that form the earth, and compare and contrast their composition and material behavior.
2_ Debate the observations that led to your understanding of plate tectonics.
3_ Describe the different types of plate boundaries.
4_ Describe the driving forces (mechanism) behind plate tectonics.
5_ Discuss the possible implications of a dynamic planet (plate tectonics) on engineering activities.
Lecture’s goals:
1_ List the layers that form the earth, and compare and contrast their composition and material behavior.
2_ Debate the observations that led to your understanding of plate tectonics.
3_ Describe the different types of plate boundaries.
4_ Describe the driving forces (mechanism) behind plate tectonics.
5_ Discuss the possible implications of a dynamic planet (plate tectonics) on engineering activities.
Lecture’s goals:
1a_ List the layers that form the earth, and compare and contrast their composition and material behavior.
3 layers: the crust, the mantle, and the core.
The crust is composed of the continental crust and the oceanic crust.
The mantle consists of the lithosphere and the asthenosphere.
The core is divided into the liquid outer and the solid inner.
Lecture’s goals:
1b_ Layers of the earth and the comparison and contrast of their composition and material behavior.
The Crust: The oceanic crust is denser than the continental crust. The mantle is denser than the crust, and the core is the densest.
Lecture’s goals:
1c_ Layers of the earth and the comparison and contrast of their composition and material behavior.
The continental crust has mostly low-density granitic rocks and is older than the oceanic crust. The oceanic crust has mostly high-density basaltic rocks.
The mantle has a temperature from 100 C to 3500 C. The mantle has a viscous behavior.
The outer core is liquid due to high tempt. The inner core tempt reaches 6000 C, solid due to high pressures.
Why the temperature of the mantle is greater than the melting point, but they are still solid?
Because of pressure
Lecture’s goals:
2_ Debate the observations that led to your understanding of plate tectonics.
Continental was boycotted because there wasn’t scientific support.
Sea-floor spreading states that the earth’s crust moves laterally away from long, volcanically active oceanic ridges. The “mid-ocean ridges” are the weak zones where new ocean floors are generated from rising MAGMA.
Continents are moved by the generations of new crust at the mid-oceanic ridges.
Sometimes, continents are split and rifted by the formation of spreading ridges.
Lecture’s goals:
What do plates float on?
The Asthenosphere (weak part of the upper mantle that behaves like a viscous solid.
The plates don’t float on lithosphere (the earth’s rigid outer shell)
Lecture’s goals:
4_ Describe the driving forces (mechanism) behind plate tectonics.
The mechanism is called: plate density/slab pull.
Note: the densest plate gets subducted.
The oceanic crust is denser than the continental crust -> the oceanic crust will always subduct compared to the continental crust.
Lecture’s goals:
3_ Describe the different types of plate boundaries.
There are 3 types of plate boundaries: convergent, divergent, and transform.
Convergent Plate Boundaries: produced by compressional forces.
- ocean-continent: accretionary wedge (ocean subducts)
- ocean-ocean: denser subducts; volcanic island arcs
- continent-continent: continental crust thickens
Divergent Plate Boundaries (oceanic spreading ridge):
-> found where continents break apart.
-> produced by extensional forces acting on the lithospheric plates
Transform Plate Boundaries: no production or destruction of material
Lecture’s goals:
3_ Describe the subduction zones of ocean-continent; ocean-ocean; and continent-continent.
ocean-continent subduction zone: oceanic plate subducts, partially melts, and the melt rises, forming a volcanic arc.
ocean-ocean subduction zone: older one descends, often forming volcanoes on the floor if sinks deep enough.
continent-continent subduction zone: an uplift of both and form high mountains.
