UNIT 1

STUDYING EARTH

Earth Facts…

• The third planet from the Sun.• One of the inner planets along with Mercury,

Venus, and Mars; these planets are made mostly of rock.

• Earth is the only planet known to support life.• Home to millions of different organisms.• These organisms may be found on land, in the

water, and in the air.

The “SPHERES” of the Earth

• Lithosphere – the layer of land that forms the Earth’s surface (rocks, soil, sand).

• Hydrosphere – all parts of the Earth that are made up of water (oceans, lakes, rivers, aquifers, clouds).

• Atmosphere – layer of air that surrounds the Earth. The atmosphere is 21% oxygen but over 78% nitrogen.

Why is there life only on Earth?

1. The presence of liquid water.• Water in the hydrosphere stores heat.• Water absorbs heat when the weather is

warm and releases it when it’s cold.• Water is found in the bodies of organisms.2. Our atmosphere.• Greenhouse Effect.3. Energy from the Sun.

Earth’s Land and Water

1. The Lithosphere• Varies in thickness from 10 – 200 km and has 3

main types of rock.a. Igneous – below the hard, solid lithosphere;

volcanic rock that has cooled.b. Sedimentary – formed by layers of sediment

that compress and harden; fossils found here.c. Metamorphic – has been transformed by heat

and pressure.

Earth’s Land and Water (cont’d)

2. The Hydrosphere • More than 70% of Earth is covered in water.• 97% of Earth’s water is salt water (contains

dissolved salts ~ 35 ppt).• Freshwater makes up 3% of the hydrosphere

(lakes, ponds, streams, aquifers); 2/3 of freshwater is frozen in glaciers and ice caps.

• Surface water vs. groundwater.

Earth’s Land and Water (cont’d)

• The Atmosphere• Envelope of gas that surrounds Earth; includes

air we breathe.• Surface>troposphere>stratosphere>

mesosphere>thermosphere.• 78% N2, 21% O2, 0.04% CO2; rest is trace gases,

water vapor, and dust particles.

Parts of the Atmosphere

• Troposphere – surface to 8 – 18 km; where most weather occurs.

• Stratosphere - reaches up to 50 km; upper layer contains ozone (O3) which is very important because it filters most of the ultraviolet (UV) rays from the Sun.

• Mesosphere & Thermosphere – mesosphere extends up to 85 km and is the coldest layer; thermosphere is the top layer and is extremely hot (2000 °C). Very little gas this high.