Chapter 1 notes
Understanding Earth
Every aspect of geology is related to our lives.
This year we will be focusing on Earth
It is a dynamic, complex planet that has changed continuously since its formation 4.6 billion years ago.
These changes and the present day features of our planet is the result of interactions among internal and external systems, subsystems and cycles.
System
A system is an assemblage of inter-related elements comprising a unified whole. From the Latin and Greek the term "system" meant to combine, to set up, to place together.
The Earth System
n Closed system
• only heat (no matter) gets exchange
n Open system
• Heat and matter gets exchange; most geologic system are complex open system.
n Changes in natural system have the tendency to go toward equilibrium: the lowest possible energy level
n Equilibrium is the condition in which the net result of the forces acting on the system are zero
The principal subsystems of Earth
n The most dynamic portion of the Earth
• Atmosphere
n Thin gaseous envelope surrounding Earth
• Hydrosphere
n Water layer dominated by the oceans
• Biosphere
n All living things on the planet
• Lithosphere
n Rocky outer shell
These subsystems are continuously interacting with each other resulting a dynamic earth that exchanges matter end energy and recycles them into different forms
What is Geology?
Geology (from Greek γη- (ge-, "the earth") and λογος (logos, "word", "reason") is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it.
Two broad areas:
• Physical geology
Study of all the earth materials (minerals, rocks) and their processes
• Historical geology
Uses the principles of physical geology to reconstruct and understand the history of the earth.
How does Geology affect our everyday life?
• Natural events
• Economy and politics
Our role
Sustainable development
"development that meets the needs of the present without compromising the ability of future generations to meet their own needs." ["Our Common Future", 1987]
• finding ways to increase prosperity and improve the quality of life while reducing overall pollution and waste;
• meeting our own needs and aspirations without doing damage to the prospects of future generations;
• reducing the environmental burden we put on our neighbors and helping to preserve common resources. ("1999 Policy Address")
The Solar System
n All bodies in the Solar System were created at the same time and from the same general material about 4.6 billion years ago.
n The center of the Solar System is the Sun, a star that generates heat by nuclear fusion.
The Sun
n Sun is the largest object of the Solar System
n Contains about 98% of the mass of the whole system.
n Solar energy is created deep within the Sun, where the temperature and pressure is high enough for nuclear reactions to take place.
Planets
The Sun’s gravitational force is large enough that all the planets are orbiting it, on the same plain, called ecliptic.
The planets are divided into two groups:
• Inner, more dense, Earth like Planets
• Outer, gaseous Planets
Inner, or Terrestrial Planets
• Mercury, Venus, Earth, Mars
• Have compact, dense rocky surface
• They have significant atmosphere, except Mercury
Mercury
• Second smallest planet in the Solar System, closest to the Sun
• Mercury has almost no atmosphere, so the sky there is always black.
• Surface has meteorite craters, and long fault systems
• Mercury has no water at all.
Venus
• The jewel of the sky, has thick swirling clouds.
• The Earth’s sister: Similar size, density, volume.
• However they are very different. No water on Venus, and thick CO2 atmosphere. Atmospheric pressure is 92 atm on the surface.
• Temperature on the surface is 482*C, caused by “greenhouse effect” from clouds.
Mars
• Commonly referred as red planet.
• Atmosphere is CO2 rich, with very little amount of Oxygen.
• No moving water present, however there is evidence of past presence of water.
• Average temperature:
-62*C
Outer, or Jovian Planets
n Jupiter, Saturn, Uranus, Neptune
n Jovian means Jupiter like.
n They have gaseous nature, although some of them might have solid core.
Earth, the blue Planet
• Earth is a Dynamic Planet inside, outside
Well developed Atmosphere, Hydrosphere, biosphere
The Atmosphere
• Less than 0.01% of the mass of the Earth
• Strong influence in Earth's evolution, life could not be possible without
• Circulation powered by solar heat
• Composition is unique in our solar system
• 78% nitrogen
• 21% oxygen (not present in early atmosphere)
• Minor amounts of carbon dioxide, argon and water vapor
• Formation of limestone in the ocean has trapped large amount of CO2
The Hydrosphere
• Total mass of water on or near the Earth’s surface
• Covers 71% of Earth’s surface
• ~98% in oceans
• 2% in glaciers, groundwater, lakes and streams (fresh water)
• The presence of water moderates climates and shapes the Earth’s surface
The Biosphere
n All life on Earth
• Animals & plants on land, in the sea and air
• Microorganisms, the most common form of life
• Forms a narrow zone near the Earth’s surface
n The diversity of life
• 1.6 million known species
n insects account for over one-half
n mammals only ~4000 species (0.025%)
• 30 million or more may exist
• Local environment controls distribution
n Temperature, pressure & chemistry
n Wide range of environmental conditions
n The biosphere as a geologic force
• Current atmosphere produced by biosphere
• Ocean composition influenced by biosphere - precipitation of calcium carbonate
• Fossils fuels
• Fossils record past Earth environments
n Current living species account for only 10% of known species throughout geologic history
Earth’s Internal Structure
n The solid Earth has a layered structure
Layers defined by composition and physical properties