Geology Magnetic Reversal Patterns

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Questions and Answers

What causes magnetic reversal in the Earth's poles?

The buildup of volcanic activity in the ocean basins.

The shifting of continents across the surface.

The changing direction of the flow of materials in Earth's liquid outer core. (correct)

The cooling of the Earth's crust over time.

What evidence led geologists to adopt the term 'plate tectonics'?

The discovery that entire plates of the Earth's crust, including continents, move. (correct)

Advancements in understanding the causes of earthquakes.

The realization that only continents move.

The identification of specific magnetic anomalies in the Earth's crust.

What phenomenon is described as the 'magnetic flip' of the Earth?

The deterioration of oceanic plates over time.

The transformation of the North Pole into the South Pole and vice versa. (correct)

The alignment of Earth's magnetic field with the solar wind.

The periodic rise and fall of sea levels influencing crust movement.

How do scientists use magnetic patterns in rocks?

To determine the ages and movement rates of mid-ocean ridge materials. Signup and view all the answers

What was a significant idea that influenced the concept of plate tectonics?

Alfred Wegener's idea of continental drift. Signup and view all the answers

What is the primary composition of the Earth's outer core?

Iron and nickel Signup and view all the answers

What phenomenon primarily facilitates the movement of the lithospheric plates?

Flowing of the asthenosphere Signup and view all the answers

What is the average thickness of the oceanic crust?

8 kilometers Signup and view all the answers

Which elements primarily make up the continental crust?

Silicon, oxygen, aluminum, calcium, sodium, and potassium Signup and view all the answers

At what temperature does the outer core reach its maximum?

2000oC Signup and view all the answers

Why does heat transfer occur?

When thermal energy moves from a warmer area to a cooler area Signup and view all the answers

What is the primary composition of the upper layer of the Earth's crust?

Granite Signup and view all the answers

What percentage of Earth's total volume does the mantle make up?

80% Signup and view all the answers

What evidence did Wegener NOT use to support his Continental Drift Theory?

Climate data Signup and view all the answers

What is the state of the inner core of the Earth?

Solid Signup and view all the answers

What layer lies beneath the lithosphere?

Asthenosphere Signup and view all the answers

Which of the following correctly describes the mantle's state?

Solid Signup and view all the answers

How thick is the Earth's outer core?

2250 kilometers Signup and view all the answers

What major landmass did Wegener hypothesize existed before the continents drifted?

Pangaea Signup and view all the answers

How does the thickness of the continental crust generally compare to the oceanic crust?

It is thicker than the oceanic crust. Signup and view all the answers

What causes the density differences between the upper and lower mantle?

Variation in the amount of iron Signup and view all the answers

What geological features provide evidence for the theory of continental drift?

Matching coastlines and mountain ranges Signup and view all the answers

Which fossil evidence indicates that certain species could not have migrated across oceans?

Cynognathus fossils found in South Africa and South America Signup and view all the answers

What characteristic of the Mesosaurus makes it unlikely to cross large ocean bodies?

It was not a strong swimmer Signup and view all the answers

Which continent's fossils provide evidence that it was once located in a warmer climate?

Antarctica Signup and view all the answers

Which feature is NOT identified as geological 'fit' evidence?

Coal deposits Signup and view all the answers

What type of animal was the Cynognathus?

A mammal-like reptile Signup and view all the answers

How do glaciers contribute to geological evidence?

By carving rocks and leaving marks Signup and view all the answers

Which of these species is known as a herbivore with a stout build and limited migration capabilities?

Lystrosaurus Signup and view all the answers

What does the presence of Glossopteris fossils in southern continents suggest about the continents?

They were likely joined at some point. Signup and view all the answers

What key discovery did Harry Hess make about the ocean floor?

It contains various geological features. Signup and view all the answers

Which process explains why the Atlantic Ocean is getting wider?

Seafloor spreading occurring faster than subduction. Signup and view all the answers

What role did SONAR technology play in understanding the ocean floor?

It mapped the features and depth of the ocean floor. Signup and view all the answers

How often has Earth's magnetic field reversed polarity, according to geophysicists?

Many times, with each reversal lasting less than 200,000 years. Signup and view all the answers

What is the significance of the mid-ocean ridge in Hess's discovery?

It is where new seafloor is formed. Signup and view all the answers

What hypothesis did Hess publish regarding ocean basins?

Seafloor spreading explains changes in ocean sizes. Signup and view all the answers

Which statement is true about Glossopteris seed characteristics?

They are large and bulky, hindering long-distance dispersal. Signup and view all the answers

Study Notes

Magnetic Properties of Seafloor Crust

Rocks of the same age in the seafloor crust exhibit magnetic polarity from the time of formation.
Surveys of the Mid-Atlantic Ridge reveal symmetrical alternating polarity stripes, indicative of historical magnetic reversals.
Magnetic reversals, or "magnetic flips," occur when the Earth's magnetic North and South Poles switch places due to changes in the flow within the outer core.
These magnetic patterns help geologists determine the ages and movement rates of materials from the mid-oceanic ridge.

Plate Tectonics

By the 1970s, geologists embraced "plate tectonics" as the foundational concept in geology, signifying that not only continents but entire plates of the Earth's crust move.
A tectonic plate may encompass a continent, portions of a continent, or undersea crust.

Earth's Crust

The Earth's crust is the outermost and thinnest layer, extending up to 32 kilometers, and up to 72 kilometers thick under some mountains.
It consists of two primary regions: continental crust (thicker, less dense, primarily granite) and oceanic crust (thinner, denser, composed mainly of basalt).
Continental crust averages 35-40 kilometers thick, while oceanic crust averages about 8 kilometers thick.

The Earth's Mantle

The mantle lies beneath the crust, extending approximately 2,900 kilometers deep and making up about 80% of Earth’s volume.
It consists mainly of silicate rocks and remains solid despite allowing seismic waves to pass through.
The mantle's composition includes silicon, oxygen, iron, and magnesium, with variations in density and composition between the upper and lower mantle.
The lithosphere (cool, rigid outer shell) is about 50-100 kilometers thick and moves on the flowing, partially molten asthenosphere beneath it.

The Core

The core has two layers: an outer core that is liquid, made primarily of iron and nickel, and an inner core that is solid with a composition similar to the outer core.
The outer core, about 2,250 kilometers thick, reaches temperatures up to 2,000°C, while the inner core has temperatures reaching approximately 5,000°C.
The movement of liquid iron and nickel in the outer core generates Earth’s magnetic field.

Heat Transfer

Heat transfer occurs from warmer areas to cooler areas due to temperature differences, following the principle that thermal energy moves from hot to cold.

Wegener's Continental Drift Theory

Alfred Wegener proposed the Continental Drift Theory in 1912, suggesting continents were once joined as a supercontinent called Pangaea.
Geological "fit" evidence includes matching coastlines and mountain ranges across continents, such as the Appalachian Mountains and the Scottish Highlands.
Fossil evidence supports the theory with species like Mesosaurus, Cynognathus, and Lystrosaurus found only on separated continents, indicating they could not have migrated across oceans.

Seafloor Spreading and Magnetic Reversal

Harry Hess discovered seafloor spreading while conducting ocean floor explorations during WWII, revealing rifts and varied topography in the ocean floor.
His research led to the understanding that new seafloor is being created at mid-ocean ridges while old seafloor is destroyed at subduction zones, explaining the dynamics of ocean sizes.
By 1963, geophysicists documented that the Earth's magnetic field had reversed polarity multiple times, providing further evidence for plate tectonics and seafloor spreading.

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Description

Explore the intriguing phenomenon of magnetic reversals in the Earth's seafloor crust with this quiz. Understand how the symmetrical pattern of polarity stripes provides insights into the age and movement of tectonic plates over time. Test your knowledge of geological processes and their implications in Earth's history.