Plate Tectonics: Earth's Structure & Tectonic Plates

Practice questions based on lecture notes covering Earth's internal layers, the differences between continental and oceanic crust, the history of tectonic theory, and the major/minor tectonic plates.

What components make up the lithosphere?

The rigid outer layer of Earth consisting of the crust and the upper mantle.

What are the characteristics of the asthenosphere?

It is the ductile (semi-fluid) region in the upper mantle beneath the lithosphere where tectonic plates float.

What is the thickness and density of continental crust?

It has a thickness of $35\text{--}70\,km$ and a density of $2.7\,g/cm^3$.

What is the composition and color of oceanic crust?

It is composed mostly of basalt (iron- and magnesium-rich) and is dark-colored with a finer texture.

Compare the density and thickness of oceanic crust to continental crust.

Oceanic crust is thinner ($7\text{--}10\,km$) and denser ($3.0\,g/cm^3$), while continental crust is thicker and less dense.

What layer of Earth generates the magnetic field?

The outer core, which is a liquid iron-nickel layer.

Why does Earth's inner core remain solid despite extreme temperatures?

It remains solid due to extreme pressure.

Which type of crust subducts and why?

Oceanic crust subducts beneath continental crust because it is denser ($3.0\,g/cm^3$).

What contribution did Abraham Ortelius make to plate tectonics in 1596?

He noticed that the continents look like they fit together like puzzle pieces.

What did Alfred Wegener propose in 1912?

He proposed Continental Drift Theory, suggesting all continents once formed a supercontinent called Pangaea.

What was Harry H. Hess's contribution to the theory of plate tectonics in the 1950s–60s?

He discovered seafloor spreading, where new crust forms at mid-ocean ridges and spreads outward.

Name the 7 major tectonic plates mentioned in the lesson.

African Plate, Antarctic Plate, Australian Plate, Eurasian Plate, North American Plate, Pacific Plate, and South American Plate.

List 5 examples of minor tectonic plates.

Arabian, Caribbean, Cocos, Indian, and Juan de Fuca (also Nazca, Philippine Sea Plate, and Scotia).

Why are earthquakes and active volcanoes frequent in the Philippines?

The Philippines is at a complex boundary where the Philippine Sea Plate meets the Eurasian (Sunda) Plate, acting as a collision zone for multiple plates.