Geochemical Model
What is the name of the Earth’s uppermost layer in the geochemical model?
The crust.
What layer of the geodynamic model is made up of the crust and the upper part of the mantle?
The lithosphere.
What are the rigid sections of Earth’s surface called in the plate tectonics theory?
Lithospheric plates.
What is the main difference between an anticline and a syncline?
In an anticline, the core has the oldest materials, while in a syncline, the core has the most modern materials.
What was the name of the supercontinent that Alfred Wegener proposed existed 300 million years ago?
Pangaea.
What type of crust is denser: oceanic or continental?
Oceanic crust.
Which layer of the geodynamic model is responsible for the movement of lithospheric plates?
The mesosphere (specifically the D’’ layer).
Who proposed the theory of plate tectonics by combining the discoveries of Wegener, Holmes, Hess, Vine, and Matthews?
Tuzo Wilson.
What type of fault is caused by extensional stress, and what effect does it have on the crust?
A normal fault, which causes thinning and lengthening of the crust.
What geographical observation led Wegener to believe South America and Africa were once joined?
The shapes of the continents appeared to fit together like puzzle pieces.
Name the two discontinuities that separate the crust, mantle, and core in the geochemical model.
Mohorovičić’s discontinuity (crust and mantle) and Gutenberg’s discontinuity (mantle and core).
What is the depth range of the asthenosphere, and what happens to plates in this layer?
From 200 km to 670 km. Plates that go down into trenches are completely melted in this layer.
What geological structure did Harry Hess discover in the ocean that supports the movement of plates?
The oceanic ridge.
What is the hinge of a fold, and what does the hinge line represent?
The hinge is the point of maximum curvature in a fold. The hinge line is the line connecting the hinges of all layers in the fold.
What is one example of geological evidence Wegener used to support his theory of continental drift?
The Caledonian mountains in Europe and the Appalachians in North America have the same rocks and structures.
What layer of the Earth in the geochemical model produces the magnetic field, and why?
The outer core; because it is made of liquid iron and nickel, which generate a magnetic field as they move.
Name the discontinuity that separates the mesosphere from the endosphere and describe the state of the outer core.
Gutenberg's discontinuity separates the mesosphere from the endosphere. The outer core is in a melted state.
What did Vine and Matthews discover about the age of basalts on both sides of the oceanic ridge?
Basalts at the same distance from the ridge have the same age, and rocks farther from the ridge are older.
Name the three types of faults and the type of stress that causes each.
What type of palaeoclimatic evidence did Wegener use to show that continents like Africa and India were once closer to the poles?
Deposits of tillite (a rock formed by glaciers) of the same age were found on continents like Africa, South America, India, Australia, and Antarctica.
What is the name of the discontinuity that separates the outer core and the inner core? And what is the key difference in the state of matter between these two parts of the core?
Lehmann’s discontinuity. The outer core is liquid, while the inner core is solid due to extremely high pressure.
What is the function of the D’’ layer at the base of the mesosphere, and how does it influence the lithospheric plates?
The D’’ layer is partially melted and less dense than the surrounding materials, causing it to flow toward the lithosphere. These movements act as the “engine” driving the movement of lithospheric plates.
What happens to the shape and position of lithospheric plates over time, and what processes at their boundaries drive these changes?
The shape and position of plates change over time due to processes such as subduction, mountain formation, and volcanism at their boundaries.
In a fold, what is the axial plane, and how does it relate to the hinge line and flanks?
The axial plane is an imaginary plane that divides the fold into two equal halves. It arises from the hinge line and separates the two flanks of the fold.
Why was the presence of fossils such as Mesosaurus and Glossopteris on multiple continents strong evidence for Wegener’s theory?
These species could not have crossed the vast oceans that separate the continents today, so their fossils found on South America, Africa, India, Australia, and Antarctica suggest the continents were once connected.