Earth Science: The Mantle and Peridotite

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Questions and Answers

What primarily determines the composition of the Earth's mantle?

The magnetic properties of the surface.

The types of minerals in peridotite. (correct)

The impact of large meteorites.

The presence of water in the mantle.

How is heat primarily transferred from the Earth's core to the mantle?

Via underground rivers of magma.

By conduction and convection. (correct)

Through radiation from surface layers.

Through magnetic field interactions.

What is the main reason the mantle is considered to be extremely hot?

The heat flows from the mantle's surface.

Heat from radioactive decay occurs in the mantle.

Heat conducted from the core is significant. (correct)

It is affected by solar radiation heat.

What happens to the mantle material as it heats up near the core?

It expands and decreases in density. Signup and view all the answers

What confirms the liquid state of the outer core?

The behavior of S-waves at the inner core. Signup and view all the answers

What percentage of the Earth's core is composed of iron?

Approximately 85 percent. Signup and view all the answers

What causes Earth's magnetic field?

Convection currents in the liquid outer core. Signup and view all the answers

What is the primary way in which mantle convection is similar to convection in water?

Both involve the movement of particles based on density changes. Signup and view all the answers

What characterizes divergent plate boundaries?

Plates move apart, leading to new seafloor formation. Signup and view all the answers

What is the result of oceanic-continental convergence?

Creation of a continental volcanic arc. Signup and view all the answers

Which of the following is a result of transform fault boundaries?

Grinding of plates past each other. Signup and view all the answers

Which phenomenon is commonly associated with oceanic-oceanic convergence?

Volcanic island arcs. Signup and view all the answers

What do transform faults primarily connect?

Segments of mid-ocean ridges. Signup and view all the answers

Which of the following supports the theory of plate tectonics?

Paleomagnetism and the age of ocean basin sediments. Signup and view all the answers

What is the primary effect of the lithosphere being broken into plates?

Continuous movement and change in shape. Signup and view all the answers

What geological feature can form as a result of continental-continental convergence?

Mountain belts. Signup and view all the answers

What significant environmental change occurred at the end of the Palaeozoic era?

Mass extinction event Signup and view all the answers

During which period did dinosaurs first appear?

Triassic Period Signup and view all the answers

Which plant groups became dominant during the Mesozoic era?

True conifers and cycads Signup and view all the answers

What geological event marked the transition from the Palaeozoic to the Mesozoic era?

Rifting of Pangaea into Laurasia and Gondwanaland Signup and view all the answers

What is one of the notable features of the Jurassic Period?

Emergence of modern birds Signup and view all the answers

Why did many forms of life, including dinosaurs, abruptly disappear at the end of the Cretaceous Period?

A mass extinction event Signup and view all the answers

What did marine reptiles like ichthyosaurs and plesiosaurs do during the Jurassic Period?

Increased in number Signup and view all the answers

What event led to the formation of the Appalachians during the Permian Period?

Geological uplift and folding of land Signup and view all the answers

What is the primary reason that the outer core remains liquid?

The production of heat by radioactive decay in the inner core Signup and view all the answers

What marked the beginning of Earth's atmosphere formation?

Outgassing from the planet's interior Signup and view all the answers

During which eons did the Precambrian span?

Archean and Proterozoic Signup and view all the answers

What process contributed to the formation of Earth's initial crust?

High velocity impacts of planetesimals Signup and view all the answers

Which of the following best describes cratons?

The core of modern continents formed during the Precambrian Signup and view all the answers

What significant event occurred around 3.5 billion years ago?

Emergence of photosynthesizing bacteria Signup and view all the answers

What was a major consequence of the decay of radioactive elements in the early Earth?

Melting of iron and nickel to form the metallic core Signup and view all the answers

What is referred to as the most recent supercontinent?

Pangaea Signup and view all the answers

What major change occurred in plant life during the Cretaceous period?

The rise of angiosperms Signup and view all the answers

During which epoch did new mammal groups such as small, horse-like animals and whales develop?

Eocene Signup and view all the answers

What significant land connection was established for North America during the Tertiary period?

Link to South America Signup and view all the answers

Which period is known as the age of mammals?

Cenozoic Signup and view all the answers

What geological principle states that current processes have operated similarly through time?

Principle of Uniformitarianism Signup and view all the answers

Which period did modern humans (Homo sapiens) first appear?

Pleistocene Signup and view all the answers

What event allowed humans to migrate to the New World?

The Bering land bridge Signup and view all the answers

What was a major consequence of the increasing prominence of grasses during the Tertiary period?

Marked changes in herbivore dentition Signup and view all the answers

Study Notes

Composition and Properties of the Mantle

The mantle consists mainly of ultramafic rock peridotite, characterized by high iron and magnesium content.
Seismic waves, heat flow data, and meteorites provide evidence of the mantle's rocky nature.
Heat within the mantle is transferred through conduction (solid materials) and convection (flowing materials).
The mantle is heated primarily by conduction from the core and convection currents that arise from the heat at the core.

Convection Mechanism in the Mantle

Convection currents in the mantle form as material near the core heats up, decreases in density, and rises.
Once the material reaches the surface and spreads horizontally, it cools and eventually sinks back into the mantle.
This cyclical movement contributes to mantle convection cells.

Structure and Composition of the Core

The Earth's core is primarily metallic, composed of approximately 85% iron and 15% nickel.
The core's metal composition is essential for Earth’s magnetic field, which wouldn't exist if the core were made of rock.
S-waves cease to exist at the inner core, confirming the core's outer component is liquid, while the inner core is solid.
Heat from the inner core prevents the outer core from solidifying and is generated by radioactive element decay.

Earth's Formation and Evolution

Earth formed about 13.7 billion years ago from materials created during the Big Bang and elements from ancient stars.
High-velocity impacts and radioactive decay increased Earth’s temperature, resulting in the melting of iron and nickel to form the core.
The early atmosphere, formed through outgassing, was primarily water vapor and carbon dioxide.

Development of Earth's Early Environment

The introduction of photosynthesizing bacteria around 3.5 billion years ago began the release of oxygen into the atmosphere.
Oceans formed as water vapor condensed, with salinity resulting from volcanic activity and erosion.
The Precambrian (spanning 4.6 billion to 542 million years ago) saw the creation of much of Earth's stable continental crust through volcanic activity and accretion.

Tectonic Plate Dynamics

Earth's lithosphere is divided into tectonic plates that float on the weaker asthenosphere below.
Divergent boundaries occur when plates move apart, leading to new seafloor at mid-ocean ridges.
Convergent boundaries result in subduction zones, forming oceanic trenches and volcanic arcs like the Andes.
Transform boundaries involve lateral movement of plates, exemplified by the San Andreas Fault.

Geological Time Periods

Pangaea, the most recent supercontinent, formed during the Permian period, leading to significant evolutionary shifts.
The Mesozoic era, or age of reptiles, was marked by the emergence of dinosaurs and other reptiles.
The end of the Cretaceous period saw the extinction of dinosaurs and significant floral changes with the rise of angiosperms.
The Cenozoic era, or age of mammals, experienced diversification in mammal species and the emergence of modern ecosystems.

Important Geological Principles

The principle of uniformitarianism states that current geological processes are consistent with those that have occurred throughout Earth’s history.

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Description

Explore the properties of the Earth's mantle, specifically focusing on peridotite. This quiz covers the evidence from seismic waves and heat flow that help scientists understand this hot, ultramafic rock. Test your knowledge on heat transfer methods within the Earth.