Chapter 17, Problem 1RQ

Summary Introduction

To review:

The following:

1. The composition of Earth’s early crust and atmosphere.

2. The processes that changed the composition of the crust and atmosphere to the present condition.

Introduction:

The outermost thin layer of a planet is known as the crust. The crust of the earth is formed from a great variety of metamorphic, sedimentary, and igneous rocks. Earth is comprised of three layers, namely crust, mantle, and core that interact with each other. Atmosphere can be defined as the gaseous envelope that surrounds the Earth.

Explanation of Solution

The main composition of the Earth’s early crust was silicon dioxide along with smaller amounts of various minerals that included carbonates as well as nitrates. Hence, it can be concluded that the crust provided a redox gradient. The early atmosphere present around the Earth’s surface was thin with a density of about 1% of today’s atmosphere.

The early atmosphere was primarily composed of carbon dioxide. The rise of living organisms that released gaseous nitrogen and oxygen changed the composition to that of the present day atmosphere. The living entities, especially microbes, play a vital role in the composition of the atmosphere present on Earth.