Download 007.DKKSP-01(INTRODUCTION)2009-08-03 07:372.7 MB

Teknologi Dan Rekayasa
Mapping And Surveing Department
INTRODUCTION
The science of Geology
 Why Geology?
 Related to our daily life, such as:
 Water and soil
 Provide guide to use of natural resources
 Provide knowledge of avoiding natural hazards
 Helping protecting the environment
• Physical geology : examines Earth
materials, understand surface and
subsurface processes
 Geology incorporates principles from physics,
chemistry, biology, engineering
Teknologi dan Rekayasa
The Science of Geology

Some historical notes about geology
 Catastrophism – mid 1600’s, James
Ussher



Sudden and violent change shape landscapes
Religious belief of Earth created in 4004 B.C.
Uniformitarianism – late 1700’s, James
Hutton



processes that operate today also operated in
past
geologic processes occur over extremely long
time
birth of modern geology
Teknologi dan Rekayasa
Earth as a system
 Earth is a dynamic planet with many
interacting parts or spheres
 Parts of the Earth system are linked
 Characterized by processes that
• Vary on spatial scales from fractions
of millimeter to thousands of
kilometers
• Have time scales that range from
milliseconds to billions of years
Teknologi dan Rekayasa
Earth as a system
 Powered by Sun - drives external processes
• Atmosphere
• Hydrosphere
• At Earth’s surface
 Powered by the Earth’s interior
• Heat remaining from Earth’s formation
• Heat generated continuously by
radioactive decay - powers internal
processes that produce volcanoes,
earthquakes, & mountains
Teknologi dan Rekayasa
A view of Earth
 Earth is a planet that is small and selfcontained, fragile, sensitive to change
 Environment is highly integrated with
interactions between air, water, rock, life
 Earth’s four spheres
• Atmosphere- air
• Biosphere- life
• Hydrosphere - water
• Solid Earth- rock
Teknologi dan Rekayasa
Atmosphere
 Gaseous environment that surrounds Earth
– provides life
 90% of atmosphere within 10 miles of Earth
surface (thin relative to radius of the solid
Earth at 4000 miles)
 Provides air for breathing and protects from
Sun’s heat and ultraviolet radiation
 Recent concern with atmosphere regarding
Ozone holes and Global Warming
Teknologi dan Rekayasa
Hydrosphere



Water makes our “Blue” plant unique –sustains life
Water in motion – Hydrologic cycle
 evaporation from oceans, precipitation from
atmosphere, run off back to ocean
 97% ocean water, 3% fresh water
 fresh water includes: surface water (lakes,
streams), ground water and glaciers
Ocean covers 71% of Earth surface -average depth of
3800 m (12,500 feet)
Teknologi dan Rekayasa
Earth’s Water Balance
Teknologi dan Rekayasa
Biosphere
Biosphere includes all life (including us!)
Extends from ocean floor to several miles into
atmosphere; however, concentrated at Earth
surface
Life responds to countless interaction with the
environment
 Successful adaptation to changing
environment – evolution of species
 Non-successful adaptation – Extinction
 Survival of the “fittest” – Darwin’s
Legacy
Teknologi dan Rekayasa
Solid Earth



Solid Earth: between atmosphere and
oceans – rocks and soil
Surface and subsurface features reveal
dynamic processes – Plate Tectonics
 Face of the Earth
 Earth’s Interior
Rock cycle - the loop that involves the
processes by which one rock type changes
to another
Teknologi dan Rekayasa
The face of Earth
 Earth’s surface - two principal divisions
• Continents
• Ocean basins
 Significant difference between the continents
and ocean basins is their relative elevations
•
•
•
continents average 2750 feet above msl
ocean floor average 12,500 feet below msl
continents average 15,250 feet above ocean
floor
Teknologi dan Rekayasa
Continents and Ocean Basins
Teknologi dan Rekayasa
Continents
 Mountain belts – linear features, active

Youngest Mountains
•
•

Circum-Pacific Belt (surrounds Pacific Ocean)
Island arcs – active volcanic mountains,
Older mountains
•
•
Appalachian – eastern United States
Urals – Russia
 Shields – continental interiors, stable craton, oldest
rocks (4 billion yrs)
Teknologi dan Rekayasa
Ocean basins
 Continental shelf – gently sloping platform
adjacent to shore
 Continental slope – steep dropoff from shelf
to deep ocean floor
 Ocean ridge system – most prominent
topographic feature on Earth (43,000 mi)
 Deep-ocean trenches – deep narrow
depressions (36,000 feet)
Teknologi dan Rekayasa
Earth’s internal structure
Layers defined by chemical composition
Crust – thin, rocky outer skin
Mantle – solid, rocky shell
Core – iron-nickel alloy center
Layers defined by physical
properties
Lithosphere – sphere of
rock
Asthenosphere – weak
sphere
Mesosphere – middle
sphere
Core – outer (liquid),
inner (solid)
Earth’s Layered Structure
Teknologi dan Rekayasa
Layers Defined by Composition

Crust
•
•


Oceanic – 7 km thick, dark igneous rock basalt,
young (<180 my), dense (3.0 g/cm3)
Continental – 70 km thick, granitic rock, old (up to
4000 my), less dense (2.7 g/cm3)
Mantle
•
•
contains 82% Earth’s volume, depth 2900 km
rock called peridotite, more dense (3.3 g/cm3)
•
•
iron-nickel w/ minor oxygen, silicon, sulfur
extreme pressure – highly dense (11 g/cm3)
Core
Teknologi dan Rekayasa
Layers by Physical Properties

Lithosphere
•
•

Asthenosphere (upper Mantle)
•
•

soft weak layer, partial melting
depth of 660 km
Mesosphere (lower Mantle)
•
•

cold, strong rock exhibits rigid behavior
5 to 250 km thick
between 660 and 2900 km depth
very hot, gradual flow of convection currents
Core (differing mechanical strengths)
•
•
Outer – liquid, generates Earth’s magnetic field
Inner – behaves as solid due to immense pressure
Teknologi dan Rekayasa
Earth’s internal structure

How do we know about the Earth’s interior?

Study of seismic wave generated by
earthquakes

Chapter 17
Teknologi dan Rekayasa
Dynamic Earth

The theory of plate tectonics
• continental drift – the idea that continents
moved about the face of the planet
• not widely accepted for more than 50 years
because driving mechanism unknown
• magnetic patterns on sea floor (found from
chasing submarines during WWII) suggested
sea floor spreading
• Plate Tectonics accepted in 1965 as driving
mechanism
Teknologi dan Rekayasa
Theory of plate tectonics
 Symmetric magnetic
pattern around ocean
spreading ridges
 Black: north magnetic
pole, white south magnetic
pole
 New ocean crust records
magnetic pole
 Crust moves away from
spreading ridges
Teknologi dan Rekayasa
Plate Tectonics



Earth’s rigid outer shell composed of numerous
slabs (plates)
• mobile, continually changing size and
shape
• create, consume, transform lithosphere
Plate boundaries
• Most major interactions among individual
plates occurs along their boundaries
Plate tectonics – first comprehensive model of
Earth’s surface and internal workings
Teknologi dan Rekayasa
Plate Boundaries
Divergent – two plates move apart, resulting in
upwelling of material from the mantle to create new
seafloor
Convergent – two plates move together with subduction
of oceanic plates or collision of two continental
plates consuming old lithosphere
Transform – located where plates grind past each other
without either generating new lithosphere or
consuming old lithosphere
Teknologi dan Rekayasa
Mosaic of Earth’s Outer Shell
Teknologi dan Rekayasa
Plate Boundaries
Teknologi dan Rekayasa
Divergent Boundaries
 Plate spreading – occurs mainly at mid-ocean ridges
(sea floor spreading), rate of 2 to 20 cm/yr
 Molten rock rises from asthenosphere through
fractures (cracks) in hard rock, encounters sea
water, cools to new rock.
 New ocean crust is continually created – oldest
ocean floor rock is 180 million years.
Teknologi dan Rekayasa
Convergent Boundaries
 Older ocean plates consumed by
subduction zone and returned to mantle
 One plate descends beneath another – high
temperature, high pressure environment
producing molten rock
 Pacific “ring of fire” – volcanic chains result
in explosive eruptions
 Mount Saint Helens, WA – 1980
 Mount Pinatubo, Philippines – 1991
Teknologi dan Rekayasa
Transform Fault Boundaries
 Plate grind past each other without creating or
consuming lithosphere
 San Andreas Fault Zone, CA – Pacific plate moving
northwest relative to North American plate
 Capable of producing strong earthquakes
•
Loma Prieta, San Francisco, CA in 1989 – 7.4
•
Northridge, Los Angeles, CA in 1994 – 6.7
Teknologi dan Rekayasa
Plate Collisions formed the Himalayas
Teknologi dan Rekayasa
Geologic time
Geologists today - accurate dates to geologic events in
Earth
history
Relative dating and geologic time scale
• Relative dating – events dates in sequence or
order without knowing their age in years
• Law of superposition – oldest sedimentary rock
layer on bottom
• Principle of fossil succession – fossils appear in a
definite order, represent time period
Absolute (radiometric) dating – Chapter 8
Teknologi dan Rekayasa
Geologic time


The magnitude of geologic time
• Age of Earth – 4.5 billion yrs (4500 million)
• Humans arrived – 0.01 million yrs
• Count one year per second 24/7– take 150 yrs
(two lifetimes) to reach 4.5 billion yrs
An appreciation for the magnitude of geologic time is
important
• many geologic processes are very gradual
• we are just a fraction of Earth’s history
Teknologi dan Rekayasa
Geologic Time Scale
Teknologi dan Rekayasa
Teknologi dan Rekayasa