Download Natural Disasters

Natural Disasters
• Earth’s Energy Sources and Systems
• Earth’s Internal Structure
• Introduction to Plate Tectonics
Earth Systems
Consequences of a “dynamic” Earth
• Earthquakes
• Volcanoes
• Mountain Building
Energy Sources for Natural Disasters
1. Gravity
The planet Earth generates a pull on every
other object in the entire universe! It is
this pull that creates weight. It is this pull
that causes an object to fall. Such a pull
is called a force. The force that causes an
object to fall is the force due to gravity.
Gravity on the earth is constant... All
objects fall equally fast. If we think
about this and take it a bit further we
come to the realization that the force of
gravity is what causes the acceleration
due to gravity. The gravitational
acceleration of the Earth (9.8 m/s2)
Gravity and Newton’s Law F = ma
(or F=mg)
•
A force applied to an object causes an
acceleration in that object. The force of
gravity is what causes the acceleration due
to gravity. (9.8m/s)
•
The more material an object has or the
greater its mass, the greater the force that
pulls on it.
•
The net force acting on an object is equal to
the product of the object's mass and its
acceleration. Consider free fall of an object
due to gravity. The force of gravity is
proportional to mass m, so we can write F =
mg, where g is the acceleration of gravity,
directed downwards..
Energy Sources for Natural Disasters
1. Gravity 2. Earth’s Internal Heat
Internal Sources of Energy
Three Sources of
the Earth’s Internal
Energy (Heat)
1. Impacts of
asteroids
2. Decay of
radioactive
elements
3. Gravitational
contraction
Origin of the Solar System
B
A
Rotating cloud of dust and gas
gathers due to gravitational forces.
Rotating mass contracts and
flattens with most of the mass in
the center.
D
C
Star ignites to form the sun.
Gases blown to outer planets.
Planets form by the accretion of stony and
iron meteorites as well as ice particles.
Early Earth is hot, hot, hot!!!
Heat Sources
•
•
Gravitational collapse
Impact Energy
•
Radioactive decay
Mantle Convection Drives Plate Motion
internal heat engine
Moving plates cause EQ’s and volcanoes!
Energy Sources for Natural Disasters
1. Gravity
2. Earth’s Internal Heat
3. Solar Energy
Solar Energy Flow
Hydrologic Cycle
Uneven Distribution of Solar Energy Causes
Severe Weather
Natural Disasters
• Earth’s Energy Sources and Systems
• Earth’s Internal Structure
• Introduction to Plate Tectonics
Chemical Differentiation of the Earth
Differentiation of the Earth…….
produces Earths’ internal structure
Crust, Mantle and Core
Radius = 6370 km
Distance to Core is ~1/2 the radius (2900 km depth)
Earth Structure
The earth today is the
product of over 4.5
billion years of
differentiation into
layers of varying
density.
The 8 most abundant
elements in the earth
are
• iron (Fe),
• oxygen (O),
• silicon (Si),
• magnesium (Mg),
• sodium (Na),
• calcium (Ca),
• aluminum (Al) and
• potassium (K),
Earth Structure - Density Stratified Layers
Earth’s Core
The earth’s core is
composed of
two parts, the
inner core and
the outer core.
The inner core is
SOLID iron (Fe)
and nickel (Ni)
and the outer
core is LIQUID
Fe and Ni.
Earth Structure - Density Stratified Layers
Mantle
Chemically the
mantle is
composed of Fe,
Mg, Si and O.
(ULTRAMAFIC
composed of Fe,
Mg silicates)
The mantle extends
from roughly 502900km below
the earth’s
surface.
Earth Structure - Density Stratified Layers
Crust
Is composed of two
types:
Oceanic Crust
(below ocean)
which is 7-10 km
thick also made of
Si, O, Fe and Mg.
(MAFIC
composed of Ca,
Fe, Mg silicates)
Continental Crust
which is 20-70km
thick made of Si,
O, Fe and Mg.
(FELSIC
composed of Ca,
Na, K silicates)
Earth Structure - Density Stratified Layers
Crust vs. Mantle
The mantle contains MORE Fe and Mg
than the oceanic crust and the oceanic
crust contains MORE Fe and Mg than
the continental crust.
Because Fe and Mg are DENSER elements,
the mantle is denser than the oceanic
crust and the oceanic crust is denser
than the continental crust.
Assume the two blocks to the left are of
equal volume and they are composed of
the same material (red atoms). If
density=mass/volume which box has the
higher density? Density can also vary
from element to element
Earth Structure - Layers of Different
Strengths
The earth is layered with
respect to physical
properties.
The crust and the upper part
of the mantle is called
the LITHOSPHERE and
it is RIGID, BRITTLE
and behaves
ELASTICALLY.
The part of the mantle
directly below the
lithosphere is termed the
ASTHENOSPHERE
which behaves like a
PLASTIC - a solid that
flows.
Upper Mantle and Crustal Structure
Oceanic
Continental
Moho
Lithosphere (or plate) = crust + uppermost, rigid part of the mantle
Natural Disasters
• Earth’s Energy Sources and Systems
• Earth’s Internal Structure
• Introduction to Plate Tectonics
Plate Tectonic Theory
• 6 large plates (e.g., Pacific Plate)
• 7-10 small plates (e.g., Arabian Plate)
Mantle Convection Drives Plate Motion
internal heat engine
Heat Sources
•
•
Original heat from formation of the Earth
Radioactive decay of U, Th, and K in the core and mantle
Plate Velocity
Up to ~17 cm/yr
Types of Plate Boundaries
1. Divergent
2. Transform
3. Convergent
Divergent Boundary
Divergent Boundary
Iceland, Mid-Atlantic Ridge
Transform Boundary
Transform Boundary
San Andreas Fault, CA
Pacific
Plate
North
American
Plate
Convergent
Boundary
Convergent Boundary
Tibetan Plateau, Himalaya Mts; SE Asia
Convergent Boundary
Andes Mts, South America