The letters following each Review Question refer to the corresponding Learning Objective from the Chapter Opener. How does a craton differ from a mountain belt? What is the difference between a platform and a shield? (G)

Short Answer

Expert verified
Cratons differ from mountain belts in their origin, stability, and age, as cratons are large, stable regions with ancient rocks, while mountain belts are younger and formed by tectonic processes. Platforms are the sedimentary cover that overlies the crystalline basement rock (shield) in a craton, characterized by horizontal layers of sedimentary rocks. Shields are the exposed, ancient, and stable crystalline basement rock of a craton, consisting mainly of igneous and metamorphic rocks and are characterized by low elevations and flat or gently undulating surfaces.

Step by step solution

01

Define Craton

A craton is a large, stable part of the Earth's continental crust that has remained relatively unchanged and undeformed for a long period of time, usually over 2 billion years. Cratons consist of two layers: a crystalline basement rock (shield) and an overlying sedimentary cover (platform).
02

Define Mountain Belt

A mountain belt is a chain of connected mountain ranges that are typically formed by tectonic processes, such as volcanic eruptions, earthquakes, and the collision of tectonic plates. Mountain belts are usually characterized by high elevations and a relatively young geological age compared to cratons.
03

Compare Craton and Mountain Belt

Cratons and mountain belts differ by their origin, stability, and age. Cratons are large, stable regions with ancient rocks, whereas mountain belts are younger and formed by tectonic processes. Cratons have a more stable and undisturbed geological history, while mountain belts are associated with more dynamic and active geological processes.
04

Define Platform

A platform is the sedimentary cover that overlies the crystalline basement rock (shield) in a craton. Platforms are made up of horizontal layers of sedimentary rocks deposited over time. These sediments usually cover an extensive area and can be several kilometers thick.
05

Define Shield

A shield is the exposed, ancient, and stable crystalline basement rock of a craton. It consists mainly of igneous and metamorphic rocks, which are older than the sedimentary rocks found in platforms. Shields are usually characterized by low elevations and flat or gently undulating surfaces.
06

Compare Platform and Shield

Platforms and shields are both parts of a craton but have different rock types and geological features. Platforms consist of sedimentary rocks that overlie the older crystalline basement rocks of shields. Platforms have a more uniform, horizontal layering, while shields are characterized by their ancient, stable, and often erosion-resistant rock formations.

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