The Lithosphere and Earth's Dynamics

Questions and Answers

What is the primary rock type found in oceanic crust?

Gneiss

Basalt (correct)

Schist

Granite

Which element is predominantly found in the composition of continental crust?

Iron

Potassium (correct)

Silicon

Calcium

What is the typical thickness range of oceanic crust?

10-20 km

15-30 km

5-10 km (correct)

25-70 km

Which statement regarding the age of oceanic and continental crust is correct?

Continental crust is older than oceanic crust. Signup and view all the answers

What defines a major tectonic plate?

Any plate over 20 million km2 Signup and view all the answers

What defines the lithosphere?

It is the rigid outer layer consisting of the crust and uppermost mantle. Signup and view all the answers

Which statement accurately compares oceanic and continental crust?

Oceanic crust has a higher density than continental crust. Signup and view all the answers

What is the primary reason that oceanic crust is denser than continental crust?

Oceanic crust consists of heavier basaltic rocks compared to lighter granitic rocks in continental crust. Signup and view all the answers

What characterizes the asthenosphere?

It has plastic properties allowing lithospheric plates to float and move. Signup and view all the answers

What is the thickness range of oceanic crust?

5-10 kilometers Signup and view all the answers

What is one characteristic that distinguishes continental crust from oceanic crust?

Continental crust has a greater average thickness than oceanic crust. Signup and view all the answers

In terms of density, how do oceanic and continental crust compare?

Oceanic crust is denser than continental crust. Signup and view all the answers

Which of the following accurately describes the composition of oceanic crust?

It primarily consists of basalt. Signup and view all the answers

Which minor tectonic plate has the largest area?

Nazca Plate Signup and view all the answers

What is the approximate area of the Cocos Plate?

2,900,000 km2 Signup and view all the answers

Which of the following statements best describes microplates?

They are usually grouped with adjacent principal plates. Signup and view all the answers

What can be inferred about the locations of earthquake epicenters and active volcanoes?

They often coincide along tectonic plate boundaries. Signup and view all the answers

Which minor plate has the smallest area?

Juan de Fuca Plate Signup and view all the answers

Why is it crucial to identify earthquake-prone areas?

To prepare and mitigate potential damage from earthquakes. Signup and view all the answers

How many major tectonic plates are typically recognized in scientific classification?

7 Signup and view all the answers

What role do earthquake epicenter maps play in geology?

They assist in mapping tectonic plate boundaries. Signup and view all the answers

Study Notes

The Lithosphere

The lithosphere is the rigid outer layer of Earth, consisting of the crust and uppermost mantle.
It plays a crucial role in plate tectonics, forming "plates" that float on the underlying asthenosphere.

Asthenosphere

The asthenosphere is a solid layer with plasticity located just below the lithosphere.
Lithospheric plates are able to move and float on this more flexible layer.

Crust Types: Oceanic vs. Continental

Oceanic crust is denser than continental crust due to its composition primarily of basalt.
Continental crust is thicker, measuring 25-70 km compared to oceanic crust's 5-10 km.

Density Comparison

Oceanic crust: denser composition (primarily iron, magnesium).
Continental crust: less dense, made mostly of granite (silica, aluminum).

Geologic Age

Continental crust is significantly older than oceanic crust, with the oldest continental crust estimated at 4 billion years.
Oceanic crust has a maximum age of around 200 million years.

Tectonic Plates

Tectonic plates are massive slabs of solid rock, either oceanic or continental, and vary greatly in size and thickness.
Major plates are larger than 20 million km², while minor plates are smaller.

Specific Minor Plates

Nazca Plate: 15,600,000 km²
Philippine Sea Plate: 5,500,000 km²
Saudi Arabian Plate: 5,000,000 km²
Caribbean Plate: 3,300,000 km²
Cocos Plate: 2,900,000 km²
Scotia Plate: 1,600,000 km²
Juan de Fuca Plate: 250,000 km²

Microplates

Often grouped with adjacent principal plates on tectonic maps, microplates are smaller tectonic units.

Scientific Basis for Plate Division

Scientists divide the lithosphere based on geological features and seismic activity, studying the distribution of earthquakes, volcanoes, and mountain belts.

Earthquake Epicenters

Earthquake epicenters are distributed predominantly along tectonic plate boundaries.
Identifying earthquake-prone areas is critical for disaster preparedness and risk management.

Active Volcanoes

The distribution of active volcanoes often coincides with earthquake epicenters, indicating tectonic activity.
This comparison suggests a strong relationship between seismic events and volcanic activity globally.

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Description

Explore the distribution of active volcanoes, earthquake epicenters, and major mountain belts in this quiz. This quiz covers key concepts related to the lithosphere and Earth's interior as part of the 2022 LCP curriculum.