1. What are the different types of lithosphere? (2 pts)
2. Which lithosphere is:
a. Older?
b. Denser? (4 pts)
3. What has been your basis in classifying the major tectonic plates as primary? (2 pts)
4. Where do active volcanoes and earthquakes most likely be found?
5. What is the scientific basis for dividing the lithosphere into plates? (4 pts)
Answer (2)
The lithosphere can be classified into continental and oceanic types, with continental crust being older and oceanic crust being denser. Tectonic plates are classified based on their size and role in geology, and most active volcanoes and earthquakes occur at plate boundaries. The division of the lithosphere into plates follows the theory of plate tectonics, which explains geological activity due to the movement of these plates.
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The lithosphere is divided into two main types:
Continental Lithosphere: This is the part of the lithosphere that consists of the Earth's continents and their extending margins. It is generally thicker and less dense compared to oceanic lithosphere.
Oceanic Lithosphere: This is the part of the lithosphere that makes up the ocean floors. It is thinner but denser compared to continental lithosphere.
To answer the questions about the lithosphere:
Older? The continental lithosphere is generally older than the oceanic lithosphere. Some continental lithosphere can be billions of years old, while the oceanic lithosphere is usually younger, typically no more than 200 million years old.
Denser? The oceanic lithosphere is denser than the continental lithosphere. This density difference is one reason why oceanic plates tend to subduct beneath continental plates at convergent boundaries.
Major Tectonic Plates Classification:
The major tectonic plates are classified as primary based on their large size and significant role in defining global plate boundaries. They include the Pacific, North American, Eurasian, African, Antarctic, South American, Indian, and Australian Plates. Their large sizes and interactions significantly influence geological activity like earthquakes and volcanic eruptions.
Location of Active Volcanoes and Earthquakes:
Active volcanoes and earthquakes are most likely found at tectonic plate boundaries. Specifically, they are common along convergent and divergent boundaries. The "Ring of Fire," encircling the Pacific Ocean, is a prime example where volcanic activity and earthquakes are frequent due to the movement of several major tectonic plates.
Scientific Basis for Dividing the Lithosphere into Plates:
The division of the lithosphere into tectonic plates is based on the theory of plate tectonics. This theory proposes that the Earth's outer shell is divided into several plates that glide over the mantle. The movement of these plates explains the distribution of earthquakes, volcanic activity, and mountain-building processes. It is supported by evidence from sea-floor spreading, distribution of fossils, and the alignment of geological features across continents.
