CHAPTER 1 Introduction to Planet “Earth” Instructor: C. Charles Dong

Personal Card Name E-mail Classes taking this semester Science/Math Background Future Major/Career Expectation of Class Expected Grade/Goal

Oceanography Geological Oceanography Chemical Oceanography Physical Oceanography Biological Oceanography

Outline General Information: earth, oceans Scientific Methods Origin of Earth, Ocean, Atmosphere Internal Structure of Earth

Overview 70.8% Earth covered by ocean Interconnected global or world ocean Oceans contain 97.2% of surface water Fig. 1.3ab

The four principal oceans Pacific Atlantic Indian Arctic Plus: Southern or Antarctic Ocean

Comparison of elevation and depth Average depth 3729 m (12,234 ft) Average elevation 840 m (2756 ft) Deepest ocean Mariana Trench 11,022 m (36,161 ft) Highest continental mountain Mt. Everest 8850 m (29,935 ft)

Fig. 1.3cd

Exe. 01-01 Name principle oceans on the earth. Do you think if “earth” is misnamed for our planet? Why?

Scientific method Observations Hypotheses Testing and modification of hypotheses Theory Probably true versus absolutely true Science is continually developing because of new observations

Scientific method Fig. 1.9

Density Density is defined as: Mass of unit divided by Volume of unit  = m / V Example: A rock has a mass of 5000 Kg Its volume is 2 m3  = m / V  = 5000 Kg / 2 m3  = 2500 Kg/m3

Density stratification Protoearth experiences density stratification Density = how heavy something is for its size Density stratification causes high density material to sink while low density material rises High density material = rock material and metals Low density material = gases

Origin of the Solar System and Earth Cloud of gas and space dust (nebula) began to contract about 4.6 billion years ago The Nebular Hypothesis

Origin of the Solar System and Earth Protoplanets were created from the nebula Protoearth was initially homogenous: Larger in size than today’s Earth Had lots of volcanic activity No continents or oceans No life

Origin of Earth’s atmosphere Partial melting resulted in outgassing about 4 billion years ago Similar to gases emitted from volcanoes Mainly water vapor Carbon dioxide, hydrogen Other gases such as methane and ammonia

Origin of Earth’s oceans Water vapor released by outgassing Condensed as rain Accumulated in ocean basins About 4 billion years ago Ice Comets were also important to adding water to the Earth system

Fig. 1.17

Ocean salinity Rain dissolves rocks Dissolved compounds (ions) accumulate in ocean basins Ocean salinity based on balance between input and output of ions Ocean salinity nearly constant over past 4 billion years

Exe. 01-02 Please describe how our solar system, the atmosphere and ocean were formed on the earth? What is density stratification? Why is sea water salty?

Earth’s internal structure Highest density material at center (core) Lowest density material at surface (crust) Earth layered Chemical composition Physical properties

Chemical composition Crust Low-density, mainly silicate minerals Mantle Mainly Fe and Mg silicate minerals Core High-density, mainly Fe and Ni

Layered Earth Fig. 1.14

Physical properties Lithosphere Asthenosphere Mesosphere Outer core Inner core

Physical properties Lithosphere Asthenosphere Cool, rigid, brittle Surface to about 100 km (62 miles) Asthenosphere Warm, plastic, able to flow From 100 km to 700 km (430 miles)

Fig. 1.15

Lithosphere Oceanic crust Underlies ocean basins Igneous rock basalt Average thickness 8 km (5 miles) Relatively high density 3.0 g/cm3

Lithosphere- Crust and Uppermost mantle fused together. Continental crust Underlies continents Igneous rock granite Average thickness 35 km (22 miles) Lower density 2.7 g/cm3

Asthenosphere Upper mantle Plastic—deforms by flowing High viscosity—flows slowly

Exe. 01-03 In terms of chemical property, how many layers does the earth have? List them. In terms of physical property, how many layers does the earth have? List them.

Life in oceans Earliest life forms fossilized bacteria in rocks about 3.5 billion years old Marine rocks Life originated in oceans?

Stanley Miller’s experiment Organic molecules formed by ultraviolet light, electrical spark (lightning), and mixture of water, carbon dioxide, hydrogen, methane, and ammonia

Fig. 1.18a

Age of Earth Radiometric age dating Spontaneous change/decay Half-life Earth is about 4.6 billion years old

Geologic time scale Fig. 1.H

Exe. 01-04 How old is the earth? When did life start on the earth? How do we know these?

Summary General Information: earth, oceans Scientific Methods Origin of Earth, Ocean, Atmosphere Internal Structure of Earth