Transcript Physical Geology

Introduction
To Physical Geology
The Science
• Geology is typically broken up into two
fields of study
– Physical Geology
– Historical Geology
Physical Geology
•
Examines the materials composing
Earth and seeks to understand the
processes that operate beneath the
surface
– It is the how and why of Geology
Historical Geology
•
Seeks an understanding of the origin
of Earth and its development through
time.
– It is the who, what, where, and when
The rock cycle
The rock cycle
- Series of processes by which rocks changes
into other types of rocks
- Illustrates various processes and paths as
earth materials change both on the surface
and inside the Earth
- What are the three main rocks ?
1- Igneous
2- Metamorphic
3- Sedimentary
The rock cycle
Fundamental Rock Types
- Igneous Rocks: solidify from melt, e.g. lava
(extrusive) or magma (intrusive)
- Sedimentary Rocks: are made at the Earth’s
surface from particle and chemical remnants
of other rocks
- Metamorphic rocks: form when other rocks
are heated, squeezed, and deformed.
Granite (igneous, intrusive)
Basalt (igneous, extrusive)
Conglomerate (sedimentary)
Shale and sandstone (sedimentary)
Limestone (sedimentary)
Sandstone (sedimentary)
Marble (metamorphic)
Quartzite (metamorphic)
Gneiss (metamorphic)
Earth as a System
–
Earth’s Four Spheres
•
Atmosphere
–
•
The air we breathe
Hydrosphere
–
•
The water we drink
Biosphere
–
•
life
Solid Earth
–
Where we live
All of these spheres interact with each other. A minor adjusting
In the properties of one could lead to drastic changes in the
Properties of the other three
Earth’s Outermost Layers
• The most dynamic portion of the Earth
– Atmosphere
• Thin gaseous envelope surrounding
Earth
– Hydrosphere
• Water layer dominated by the oceans
– Biosphere
• All living things on the planet
– Lithosphere
• Rocky outer shell
The Atmosphere
Composition is unique in solar •
system
78% nitrogen –
21% oxygen (not present in early –
atmosphere)
Minor amounts of carbon dioxide, –
argon and water vapor
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 Biosphere
• All life on Earth
– Animals & plants on land, in the sea
and air
– Microorganisms-the most common
form of life
– Evolved within narrow zone near the
Earth’s surface
Earth’s Internal Structure
• Solid Earth has a layered structure
– Layers defined by composition and
physical properties
– Compositional layers
• crust - mantle - core
– Physical layers
• lithosphere - asthenosphere mesosphere - outer core - inner core
Compositional Layers
• Crust
– Outermost compositional layer
– Definite change in composition at the
base of the crust
– 2 types:
• Continental crust
• Oceanic crust
Compositional Layers
• Mantle
– Largest layer in the Earth
• 2900 km thick
• 82% by volume
• 68% by mass
– Composed of silicate rocks with
abundant iron and magnesium
• Density ranges from 3.2 to 5 g/cm3
Compositional Layers
• Core
– Central mass about 7000km in
diameter
– Average density of 10.8 g/cm3
– 16% by volume, 32% of mass
– Indirect evidence of composition
• Metallic iron
Physical Layers
• Lithosphere
– Crust + upper portion of the mantle
– Solid & rigid
– Thickness ranges from 10 km
beneath oceans to 300 km in
continental areas
• Crust
– Continental crust
• Thick - up to 75 km
• Lower density - 2.7 g/cm3
• Strongly deformed
• Much older - may be billions of years old
• Crust
– Oceanic crust
• Thinner - about 8 km
• More dense - 3.0 g/cm3
• Comparatively undeformed
• Much younger - < 200 million years old
Physical Geology
• Earth’s Systems
– Atmosphere
• gases that surround the Earth
– Hydrosphere
• water on or near Earth’s surface
– Biosphere
• all living or once-living materials
– Geosphere
• solid, rocky Earth
Earth’s Interior
• Compositional Layers
– Crust
• Very thin outer rocky shell of
Earth
• Variable thickness
– Mantle
• Hot solid
• Special “plastic” zone
• Fe-, Mg-, Si-rich minerals
– Core
• Outer core
– liquid
– mostly iron
• Inner core
– solid
– mostly iron
Earth’s internal layers
The Earth in Space
Age of the Earth = 4.5 Billion years
[4,600,000,000 years]
Age of the Universe = 14 Billion years
Earth Compared to Other
Planets
• The Solar System
– The inner planets
• Rocky planets near the Sun
• Mercury, Venus, Earth & Mars
– The outer planets
• Giant gaseous planets
• Jupiter, Saturn, Uranus, Neptune
– Pluto, a small icy minor planet
Origin of the Solar System
• Gravitational collapse of gas & dust
cloud [nebula]
– Rotation around a central mass
– Disk shaped cloud
– Temperature variations segregated
matter
– Small particles accreted into larger
planetesimals, planets
How do we
Know this?
• Differences between inner and outer
planets:
– Density
– The rocky inner planets=densities of
3 g/cm3 more
– The gaseous outer
Planets=densities
of 1.6 g/cm3 or less