Wikibooks: High School Earth Science/Water on Earth

• Format: Book
• Language: English
• Subjects: Greenland; Antarc*; Antarctica
• Online Access: https://en.wikibooks.org/wiki/High_School_Earth_Science/Water_on_Earth

TOC right Water is a simple compound made of two atoms of hydrogen and one atom of oxygen bonded together. More than any other substance on the Earth water is important to life and has remarkable properties. Without water life could probably not even exist on Earth. When looking at Earth from space the abundance of water on Earth becomes obvious mdash see Figure 13.1. On land water is also common it swirls and meanders through streams falls from the sky freezes into snow flakes and even makes up most of you and me. In this chapter we ll look at the distribution of water on Earth and also examine some of its unique properties. =Lesson Objectives= Describe how water is distributed on Earth. Describe what powers the water cycle and how water moves through this cycle. =Distribution of Earth s Water= As Figure 13.1 makes clear water is the most abundant substance on the Earth s surface. About 71% of the Earth s surface is covered with water most of which is found in the oceans. In fact 97% of Earth s water nearly all of it is in the Earth s oceans. This means that just 3% of Earth s water is fresh water water with low concentrations of salts (Figure 13.2). Most freshwater is found as ice in the vast glaciers of Greenland and the immense ice sheets of Antarctica. That leaves just 0.6% of Earth s water that is freshwater that humans can easily use. Most liquid freshwater is found under the Earth s surface as groundwater while the rest is found in lakes rivers and streams and water vapor in the sky. =Three States of Water= Water is a special substance. It is abundant on Earth and frequently appears as a gas liquid and solid. It is one of the few substances on Earth that is frequently found in all three phases of matter. Moreover it can readily cycle through the globe the same molecule can travel through many different regions on Earth. Part of the reason that water is unique is because of its melting point and boiling point. Under normal atmospheric conditions water freezes at 0 deg C (32 deg F) and boils at 100 deg C ...