Earth and Space Science Unit 1 (Plate Tectonics)

continental drift

the gradual movement of continents across the Earth's surface due to tectonic forces.

Pangaea

The supercontinent that existed during the late Paleozoic and early Mesozoic eras, which eventually broke apart to form the continents we know today.

Isochron

A line on a map connecting points of equal age of geological features, often used to represent the age of rock layers or ocean floor.

Magnetic Reversal

A change in the Earth's magnetic field where the positions of magnetic north and south are switched, occurring over geologic time.

Magnetometer

An instrument used to measure the strength and direction of magnetic fields, commonly employed in geological surveys to detect magnetic anomalies in rocks.

Paleomagnetism

The study of the record of the Earth's magnetic field in rocks, sediment, or archaeological materials, which provides information about the historical changes in Earth's magnetic field and plate movements.

Seafloor Spreading

The process by which new oceanic crust is formed at mid-ocean ridges and gradually moves away from the ridge, leading to the expansion of ocean basins.

Convergent Boundary

A tectonic plate boundary where two plates collide, often resulting in one plate being forced beneath the other, leading to mountain formation or volcanic activity.

Divergent Boundary

A tectonic plate boundary where two plates move apart from each other, often resulting in the formation of new crust as magma rises to the surface, typically found at mid-ocean ridges.

Rift Valley

A lowland region formed by the divergence of tectonic plates, characterized by steep walls and often associated with volcanic activity.

Subduction

The process by which one tectonic plate moves under another and sinks into the mantle, often causing earthquakes and volcanic activity.

Theory of Plate Tectonics

A scientific theory that explains the movement of the Earth's lithosphere, which is divided into tectonic plates that float on the semi-fluid asthenosphere, leading to geological phenomena such as earthquakes, volcanic activity, and mountain formation.

Transform Boundary

A type of plate boundary where two tectonic plates slide past each other horizontally, often causing earthquakes.

Ridge Push

A tectonic process where the elevation of a mid-ocean ridge causes the surrounding tectonic plates to be pushed away from the ridge, contributing to plate movement.

Slab pull

A tectonic process where a dense oceanic plate sinks into the mantle at a subduction zone, pulling the rest of the plate along with it.

Briefly describe 3 (three) types of evidence from the early part of the 1900s to support the theory of continental drift

1. Fossil Evidence: Identical fossils of plants and animals, such as the Mesosaurus (a freshwater reptile) and the plant Glossopteris, were found on continents that are now widely separated, like South America, Africa, and Antarctica. This suggested these continents were once connected, allowing species to inhabit continuous land areas.

2. Geological Evidence: Similar rock formations, mountain ranges, and geological structures were found on continents that are now distant from each other. For example, the Appalachian Mountains in North America align geologically with the Caledonian Mountains in Scotland and Scandinavia, indicating they were once part of the same landmass.

3. Climatic Evidence: Evidence of past climates, such as glacial deposits and striations (scratches in rocks caused by glaciers), were discovered in now-tropical regions like India, Africa, and South America. This indicated that these continents were once located closer to the South Pole, supporting the idea that continents had drifted over time.

4o

Describe evidence of seafloor spreading and explain the significance of magnetic striping and isochrons

• Magnetic Striping: As molten rock rises at mid-ocean ridges and solidifies, iron-rich minerals within the rock align with Earth's magnetic field. Since Earth's magnetic field has reversed many times throughout history, these rocks record a pattern of magnetic "stripes" with alternating normal and reversed polarity. These symmetrical stripes are found on both sides of mid-ocean ridges, providing strong evidence that new crust is continuously formed at the ridges and spreads outward.

• Age of Oceanic Crust (Isochrons): Isochrons are lines on maps that connect points of equal age on the seafloor. Studies show that the youngest rocks are located at the mid-ocean ridges, while the rocks become progressively older as you move away from the ridges. This age pattern supports the idea of seafloor spreading, with new crust forming at the ridges and older crust pushed outward over time.

• Distribution of Earthquakes and Volcanoes: The majority of earthquakes and volcanic activity occur along mid-ocean ridges and subduction zones. This distribution aligns with the theory that tectonic plates are moving apart at ridges (creating new crust) and converging at subduction zones (destroying old crust).

How is seafloor spreading related to continents spreading apart?

Seafloor spreading occurs at mid-ocean ridges where new oceanic crust forms as magma rises from the mantle. As the seafloor spreads, it pushes tectonic plates apart, causing the continents sitting on these plates to move away from each other.

How does the theory of plate tectonics account for the changing features on Earth’s surface?

Plate tectonics explains that Earth’s surface is divided into large plates that move due to mantle convection. This movement causes the formation of mountains, earthquakes, volcanoes, ocean trenches, and other geological features as plates interact at their boundaries.

What are the four layers of Earth’s interior, including the crust?

The four layers are:

1. Crust – The outermost, solid layer where we live.

2. Mantle – A thick, semi-solid layer where convection currents occur.

3. Outer Core – A liquid layer made of molten iron and nickel, responsible for Earth’s magnetic field.

4. Inner Core – A solid sphere composed mainly of iron and nickel under extreme pressure.

What are the important characteristics of each of Earth’s four layers?

• Crust: Thin, brittle, made of continental and oceanic types.

• Mantle: Hot, semi-solid rock that flows slowly due to convection currents.

• Outer Core: Liquid metal generating Earth’s magnetic field.

• Inner Core: Solid due to immense pressure, very hot, mainly iron and nickel.

What are the three types of plate boundaries?

• Divergent Boundaries

• Convergent Boundaries

• Transform Boundaries

How would you describe each of the three types of plate boundaries?

• Divergent: Plates move apart, creating new crust (e.g., mid-ocean ridges).

• Convergent: Plates move toward each other, causing subduction or mountain formation.

• Transform: Plates slide past each other, causing earthquakes (e.g., San Andreas Fault).

What are the three kinds of convergent boundaries?

• Oceanic-Continental Convergence

• Oceanic-Oceanic Convergence

• Continental-Continental Convergence

How would you describe each type of convergent boundary?

• Oceanic-Continental: Denser oceanic plate subducts under the continental plate, forming trenches and volcanoes.

• Oceanic-Oceanic: One oceanic plate subducts under another, creating deep-sea trenches and volcanic island arcs.

• Continental-Continental: Two continental plates collide, crumpling and forming mountain ranges like the Himalayas.

How is a fault formed?

A fault forms when rocks break and slip along a fracture due to stress from tectonic forces, often causing earthquakes.

How is a rift valley formed?

A rift valley forms at divergent boundaries when the Earth's crust stretches and thins, causing it to sink between two parallel faults.

How is an ocean trench formed?

An ocean trench forms at convergent boundaries where one tectonic plate subducts beneath another, creating a deep depression in the seafloor.`

How is a subduction zone formed?

A subduction zone forms when an oceanic plate is forced beneath another plate due to convergent movement, leading to volcanic activity and trenches.

How can you identify different types of boundaries on a world map showing tectonic plates?

How can you identify different types of boundaries on a world map showing tectonic plates?

How would you label a diagram of a cross-section of Earth’s interior?
A14: From the outermost to innermost:

1. Crust

2. Mantle

3. Outer Core

4. Inner Core

: How does convection in the mantle cause plate movement?

Mantle convection occurs as hot material rises and cooler material sinks, creating currents that drag tectonic plates along the surface.

What do the terms "ridge push" and "slab pull" mean in the context of plate movement?

• Ridge Push: The force exerted by rising magma at mid-ocean ridges pushes plates apart.

• Slab Pull: The force of a dense, subducting plate pulling the rest of the plate along as it sinks into the mantle.