Question

Each phrase below describes a vocabulary term from the list. Write the term that matches the phrase describing it. Composed of oceanic or continental crust and upper mantle

Short answer

Lithosphere

Step-by-step solution

Understanding the Components

The exercise mentions 'oceanic or continental crust' and 'upper mantle'. We need to identify the vocabulary term that includes these components.

Identifying Vocabulary Category

The vocabulary term we are looking for is likely within the realm of geology, specifically related to Earth's layers.

Matching to Geology Terms

One of the major terms used to describe the combination of crust and upper mantle is the 'lithosphere', which includes both oceanic and continental crust along with the rigid upper part of the mantle.

Verifying Term Definition

The lithosphere is defined as the rigid outer part of the Earth, which is made up of the crust (both oceanic and continental) and a portion of the upper mantle. This matches the description given in the exercise.

Key concepts

Oceanic Crust

The oceanic crust forms the outermost shell of the Earth beneath the ocean basins. Despite being relatively thin, typically around 5-10 kilometers thick, it plays a crucial role in supporting oceanic ecosystems and processes. Like the various layers of a cake, the oceanic crust is only one slice of the Earth's structure, but without it, the planet wouldn’t be quite the same.

• It is primarily composed of basalt, a dark volcanic rock rich in magnesium and iron.
• Due to its composition, it is denser compared to the continental crust.
• New oceanic crust forms at mid-ocean ridges, where tectonic plates pull apart, allowing magma to rise and cool.

Understanding the dynamics of the oceanic crust is essential for appreciating geological processes like earthquakes, and the formation of ocean features such as ridges and trenches.

Continental Crust

The continental crust forms the semi-permanent surface layer of our continents. Unlike the transient oceanic crust, the continental crust is much older and thicker, ranging from around 30 to 50 kilometers in thickness.

• It mainly consists of lighter rocks like granite, rich in silica and aluminum.
• Despite its thickness, it is less dense than the oceanic crust, which is why continents appear higher than ocean floors.
• The age of continental crust can exceed billions of years, revealing a vast geological history.

The continental crust not only supports terrestrial life but also holds clues about Earth's formation, tectonics, and evolution.

Upper Mantle

The upper mantle is a layer of Earth that lies just beneath the crust, forming part of the lithosphere along with the crust. It extends from around 30 kilometers below the surface down to about 410 kilometers. Despite being composed of solid rock, it behaves in a somewhat plastic manner, due to higher temperatures and pressures experienced at that depth.

• Made primarily of silicate minerals like olivine and pyroxene, it is richer in iron and magnesium compared to the crust.
• The upper mantle is crucial in the convection processes that drive tectonic plate movements.
• It is involved in the recycling of lithospheric plates, as subducted slabs descend into the mantle.

Understanding the upper mantle helps in comprehending phenomena such as volcanic eruptions, plate tectonics, and how heat flows within Earth.