Plate Tectonics: A Unifying Theory Quiz

Plate Tectonics: A Unifying Theory

• Plate tectonics is the unifying theory of geology, explaining seemingly disparate geological phenomena.
• It helps understand processes like volcanoes, earthquakes, and mountain building.
• This theory proposes that Earth's outer part (lithosphere) is made of plates that move relative to one another.
• Continents and ocean basins are part of the lithosphere and have moved throughout Earth's history.

Quiz Information

• There is a quiz called Quiz 2 on UM Learn.
• The quiz is worth 10 points.
• Unlimited attempts are allowed, but only the highest score will be recorded.
• The quiz is due by Friday, January 17th at 11:59 PM.

Lecture Objectives

• The previous lecture covered the rock cycle.
• This lecture will examine the evidence for continental drift.
• This lecture will discuss the theory of plate tectonics.

Earth as a Dynamic Planet

• Earth is a dynamic and evolving planet.

Quiz 1 Topics

• The quiz covers a wide range of topics, including geological processes, geology in society, meteoric impact craters, magnetic reversals, new galaxy formations, and the anthropocene, continental drift, and continental rifting.

Continental Drift Hypothesis

• In 1912, Alfred Wegener proposed that a single supercontinent (Pangaea) broke apart to form the modern continents.
• Alexander Du Toit further developed these ideas in 1937.
• Evidence for continental drift includes continental fit, similarity of rock sequences, mountain ranges, glacial evidence, and fossil evidence.

Continental Fit Evidence

• The continents appear to fit together like pieces of a puzzle.

Similarity of Rock Sequences

• Similar rock sequences and mountain ranges are found on continents that were once joined.

Glacial Evidence

• Glacial evidence (glacial striations) suggests that continents that are currently separated were once in a polar region.

Fossil Evidence

• Similar fossils have been found on continents that are now separated, indicating that they were once connected.

Driving Forces of Plate Tectonics

• Plate tectonics is driven by several forces including convection cells, ridge push, and slab pull.
• The theory of convection cells explains movement in the mantle.
• Ridge push occurs as the elevated mid-ocean ridges push adjacent plates away from the elevated area.
• Slab pull occurs because denser oceanic lithosphere sinks into the asthenosphere.

Misconceptions about Convection

• The conceptual model of convection has been refined. Convection cells alone are not believed to drive plate motion.

Plate Driving Forces: Ridge Push

• Ridge push occurs due to the gravitational energy associated with the elevated topography of mid-ocean ridges.

Plate Driving Forces: Slab Pull

• Slab pull occurs because old oceanic lithosphere is denser than the underlying asthenosphere, and it sinks.

Earth's Magnetic Field

• Earth has a magnetic field.
• Earth's magnetic poles do not exactly line up with the geographical poles.
• Magnetic reversals, where the poles switch, occur.
• Magnetic anomalies are useful for reconstructing plate positions.

Seafloor Spreading

• Seafloor spreading is confirmed by magnetic anomalies along with the spreading ridges.
• The crust is youngest near spreading ridges; the oldest is farthest away.

Plate Positions

• Plate positions can be reconstructed based on data from Magnetic Anomalies.

Earth's Structure

• The Earth is divided into distinct layers: the core, mantle, and crust
• The core is made primarily of iron and some nickel, and is divided into a solid inner core and a molten outer core.
• The mantle surrounds the core. It's divided into the upper, asthenosphere, and lower parts and is made up primarily of peridotite and olivine.
• The crust is the outermost layer of Earth and is relatively thin.