Exam 2
Hurricane Lenny
"Wrong Way Lenny" - west to east - occurred in November, was expected - not in wrong direction tho
Metamorphic rock
"meta" (change) and "morph" (form) - rock is moved into envt. in which the minerals which make up the rock become unstable and out of equilibrium with the new environmental conditions - In most cases, this involves burial which leads to a rise in temperature and pressure - metamorphic changes in the minerals always move in a direction designed to restore equilibrium - Any rock can become a metamorphic rock, including another metamorphic rock (can become a different metamorphic rock)
condensation of water
releases a large amount of heat.
pyroclastics (ejecta)
thrown from the volcano - cool very quickly
what contributes to storm surge?
- Action of winds piling up the water, both around center & w/ forward motion. - Waves pushing water inland faster than it can drain - Low pressure of eye sucking water higher.
Regional
- Areas of great amounts of pressure (during mountain-building) - high temperatures
Ocean Floor Magnetic Anomalies
- Discovered in oceans by ships dragging magnetometers (1940s and 1950s) - Stripes symmetrical around mid-ocean ridges - Due to magnetism of new ocean floor basalts (reversed and normal) - Sea-floor spreads like 2 diverging conveyor belts w/ new magma extrusion between them - Same patterns around ridges worldwide - Stripe widths vary due to different spreading rates at ridges
Wegener's Ancient Climates
- Evidence of ancient glaciers found in areas that are presently tropical (central Africa) - Coals (formed in tropical climates) in presently cold climates - No ancient glaciers in Northern Hemisphere
Opinions of
- Few supporters - mostly European and African geologists - Ridiculed by American geologists - Can't "sail" continents through oceans, no mechanism to explain movement - Suggested land bridges as the answer to explain fossils - Interest in continental drift revived in 1950s, leading to Plate Tectonics
Clastic Sediments
- Formed from erosion of other rocks - Most sediments are carried by rivers & deposited in great amounts in ocean - Under great pressure, these particles are cemented together - Classified by particle size
Sedimentary Rocks
- Formed from sediments that settle through water in great amounts and are cemented together under great pressure - Covers 80% of the Earth's crust - Fossils form in sedimentary rocks
Rich in silicates
- Lots of feldspar, quartz, and other silicates - Lighter color - More viscous - extrusives form steep volcanoes - Continental crust
Poor in silicates
- Lots of iron and magnesium rich minerals - Darker color - Less viscous - extrusives form large flows - Oceanic crust
Contact
- Near magma chambers (plutons) - Rocks in "contact" or near-contact with the magma are baked - NEW minerals are formed - Rocks do not conduct heat well (they are good insulators) so the zone of contact metamorphism is usually relatively narrow
Outer Core
- Plastic or semi-fluid - Composed mostly of iron - Movement (convection?) generates Earth's magnetic field
Mantle of Earth
- Plastic or semi-fluid - Split into the upper & lower mantle - Most of earth's mass
Wegener's Alignment of Mountain Ranges
- Ranges with the same ages of deformation on opposite sides of ocean - Appalachians (N. America) line up with Caledonides (Britain & Scandinavia) & with African belt of deformation
Types of Common Igneous Rocks
- Rhyolite - Granite - Basalt - Gabbro
Inner Core
- Solid - Composed mostly of iron - Temp. @ center = 7500 K (hotter than surface of Sun)
Factors that affect where hurricanes go
- Steering winds - trade winds and westerlies - High-pressure weather systems - Ex: Bermuda high - Low-pressure weather systems - Storm's place and time of origin
hurricane
- Sustained winds of 74 mph (64 knots - Pressures below 980 millibars - Eye is present - Categorized on scale of 1-5 based on wind speed & resultant destructive potential - Saffir-Simpson Scale - counter-clockwise
tropical depression
- Tropical wave develops a closed circulation with maximum sustained winds of less than 39 mph (33 knots) - Distinct center of low pressure (above 1,000 millibars) - Given a number by National Hurricane Center (NHC)
Low-pressure weather systems
- Troughs - Lows - Another storm
cold air mass above requirement
- Unstable atmosphere; increases the likelihood of convection - Strong updrafts that lift the air and moisture upwards
Crust of Earth
- Varies considerably in thickness (thinner under the oceans/thicker under the continents) - Solid and brittle - Least dense layer
hurricane eye wall
- Very strong winds - Can undergo replacement cycles - Ring of intense thunderstorms/rain surrounding the eye (worst part of a hurricane)
Storm's place and time of origin
- Water temperature - Position of the ITCZ
continental shelf
- Width varies from almost non-existent in one part of southern Florida to over 800 kilometers north of Siberia in the Arctic Ocean - A structural part of the continental land mass
tropical storm
- Winds exceed 38 mph - Distinct low pressure system (below 1000 millibars) - Spiral pattern in satellite images - NHC gives it a human name
Iron
- abundant & right density to be in core of Earth - It conducts electricity, which is necessary to generate a magnetic field.
diagram of a hurricane
- can be blocked off
Evidence of tectonic plates
- continental drift - sea floor spreading
Physical Properties of Minerals
- hardness - streak - color - density - cleavage
As storm surge hits land, it...
- is pushed on top of the existing ocean waters. - is added on to the height of the existing tide. - does not hit as one large wave but as a slower increase in the sea level (more rapid as eye approaches) - can push up bays and rivers
A hurricane weakens when...
- it moves over land - it moves over cold water - Sahara dust - strong upper level winds
volcanoes and earthquakes have in common
- occur in same locations - release vast amounts of energy in the form of movements of vast amounts of material
Factors Affecting Storm Surge
- shape of coastline - slope of underwater ocean floor near the coast - magnitude of hurricane
hurricane eye
- smaller eye means more powerful - 20-50 km in diameter - Relatively warm - Light winds - Clear/broken clouds - point of lowest pressure
Requirements for a hurricane to occur
- warm ocean water (water @ 80ºF (26oC) in upper 200 ft) - warm, humid air (produced by warm ocean water) - not on Equator - cold air mass above - weak upper level horizontal winds
Alfred Wegener
- was a meteorologist - spent time stationed in Greenland with plenty of time to think - Proposed "continental drift"
4 stages in formation of hurricane
1) tropical disturbance (tropical wave) 2) tropical depression 3) tropical storm 4) hurricane
Deepest hole drilled
12.3 km - crust = 40km
What month is ocean temp. in VI the greatest?
August / September
The Rock Cycle
A series of processes on the surface and inside Earth that slowly changes rocks from one kind to another
Explosive Vs. Non-Explosive Volcanoes
Due to the mineral composition of igneous rocks
damage caused by hurricanes
Due to wind and water - More commonly visible damage is from wind. - can be devastating to buildings and vegetation - Torrential rains can cause devastating flooding and mud slides, especially in areas with hills or mountains.
High pressure acts like
a wall - hurricanes must go around it
plate tectonics
Explains volcanoes, earthquakes, patterns of mountains, distribution of fossils, etc. - now widely accepted by geologists
Wegener's Coastline Fit
Fit of coastlines between countries show that they were once one land mass
Flat topped submarine peaks => evidence of seafloor spreading
Form as volcanic islands near mid-ocean ridges Beveled off near ridge by wave erosion As seafloor migrates away from ridges, lithosphere cools, becomes more dense, and sinks.
Rift discovered at crest of mid-ocean ridge
Formed as crust pulls apart
Clastic Particles and the Corresponding Rocks
Gravel --> Conglomerate Sand --> Sandstone Silt --> Siltstone Clay --> Claystone
organic rock
Growth in place - Accumulation of sedimentary debris caused by organic processes - Shells, bones, and teeth (calcium) - These bits of calcium can pile up on the seafloor and accumulate into a thick enough layer to form an "organic" sedimentary rock - Limestone, lignite, & bituminous coal can form this way -Ex: coral reefs
Deep-ocean studies
High mountain ranges (mid-ocean ridges) discovered 1940s => world-surrounding feature
Warm water requirement
If the ocean water were cooler there would be less evaporation of water. Then there would be less rising of warm air and less condensaion of water at cloud level. The air pressure at the surface of the ocean would be higher. The wind speed blowing to the low pressure center would be slower.
Where are rocks located?
In Earth's crust
Rocks are further subdivided by
Mineral composition - what minerals are present in large quantities Texture - What is the size of the mineral crystals (grains)
magma
Molten rock below Earth's surface - intrusive (below surface) - gathers in large bodies called plutons - may become lava - cools slowly - forms large crystals
lava
Molten rock that is above Earth's surface - Extrusive (above surface) - expelled from a fissure or a volcano - begins as magma - cools rapidly - forms small or no crystals
New evidence to support Wegener's idea
Ocean Floor Magnetic Anomalies
Wegener's Similar Rock Sequences
Pattern of rock layers between countries
Types of Metamorphism
Regional and contact
Mineral Composition of Igneous Rocks
Rich & poor in silicates
Additional evidence of what happens in Earth's interior
Seismic waves of earthquakes & material ejected from volcanoes
Hurricane season in VI
September
what makes it easier to forecast hurricanes?
Strong steering winds
What is the mechanism that causes a tropical depression over warm water to spontaneously strengthen?
Surface water evaporates, making warm air moist. Rising moist air cools; water vapor condenses at cloud level. This RELEASES HEAT into the cloud-level air! The heated air rises faster, creating a lower pressure in the space it leaves. This lower pressure sucks more moist air from sea level up faster, which condenses & releases more heat. More air leaving the surface faster makes the low pressure lower, so wind blows to it faster
tropical disturbance
System of clouds, showers, and thunderstorms - Originates in intertropical convergence zone (ITCZ) - body sustained for 24 hours - Trough of low pressure (not distinct center) - Moves east to west - often from west coast of Africa toward Caribbean Sea
What causes winds to blow in a circle during formation of a tropical depression?
The Coriolis Force - It deflects the winds as they try to fill in the low pressure
strong upper level winds (wind shear)
The two winds blowing in opposite directions, but slightly offset from each other, produce a "shearing" force on the hurricane. - common in El Nino
1962 Hess proposed "sea-floor spreading"
Thermal convection cells with continents passive "passengers"
Largest losses of life and greatest damage is due to
Water!
what makes it harder to forecast hurricanes?
Weak steering winds
Why is Earth's center hot?
When the Earth formed ~4.5 billion yrs ago from particles accreting (clumping together), a huge amount of heat was released from gravitational energy and the decay of radioactive elements. - Hot enough to melt Earth
Tropical Cyclone
a closed surface wind circulation around a low pressure center that develops over tropical waters - NOT a front
pure chemical compound
a definite chemical structure which gives rocks unique physical properties
Low pressure acts like
a magnet - draws hurricanes towards it
minerals
building blocks of rocks - naturally occurring (not man-made) - inorganic - solid - pure chemical compound
southern hemisphere direction of wind
clockwise
positive feedback system
conditions that cause a disturbance to get stronger
Location of earthquakes and volcanoes
correspond to the edges of tectonic plates
Northern hemisphere direction of wind
counter-clock wise
Earth's layers
crust, mantle, outer core, inner core
storm surge
damage by water - increase in sea level caused by storm
tropical cyclone moves from
east to west in the tropical trade winds.
compounds are composed of
elements
anatomy of a hurricane
eye & eye wall
Igneous rock
formed when molten rock cools and solidifies
pumice
frothy volcanic glass
Layer of Earth gets ______ the closer you get to the center
hotter
cleavage
how does it break...along planes?
High-pressure systems and Coriolis effect can cause
hurricanes to curve north
Rock Classification
igneous, sedimentary, metamorphic
When the Earth was still molten,
iron sank to the center, silicates rose to the mantle and crust
Forward motion of the storm SUBTRACTS to the wind velocity on which side?
left side of a storm
Foliation
minerals align under pressure
rock
mixture of minerals
inorganic
not part of or a product of a [once] living organism
Nickel
often found with iron in meteorites; likely to be in the core as well.
most common elements in crust
oxygen and silicon
clastic rock
particles deposited by water, wind, or ice - basic sedimentary rock. - accumulations of pieces of broken up (eroded) rock (clasts) which have piled up and been "lithified" (turned to rock) by compaction and cementation
chemical rock
particles precipitate from solution - Can form when water conditions change causing solids to precipitate out of solution - Can form when standing water evaporates, leaving dissolved minerals behind
Wegener's fossils
plant & animal fossils similar across oceans
The crust of the earth is cracked into fragments, called ________, which move slowly.
plate tectonics
hurricane over cold water
receives less energy than from warm water.
As a hurricane moves north, it enters what region?
region where westerly winds dominate and then it starts to move eastwards.
Forward motion of the storm ADDS to the wind velocity on which side?
right side of a storm
evidence of continental drift
scientists noted similarities between plant fossils and glacial evidence in diff. countries
The most common minerals
silicates -contain silicon and oxygen -most common silicate = quartz
Common metamorphic rocks
slate, schist, gneiss, and marble
hurricane over land
stops receiving large amounts of warm water.
Wegene's evidence
supported his claim of continental drift
Cyclones are NOT at
the Equator
Ocean Floor Topography
the natural and artificial features existing on the ocean floor - Deep-ocean studies - Flat topped submarine peaks --> evidence of seafloor spreading - Rift discovered at crest of mid-ocean ridge - 1962 Hess proposed "sea-floor spreading"
viscous
thick and adhesive, like a slow-flowing fluid Ex: molasses
Earth's overall average density is about
twice as great as the average density of the rocks of the crust. - So, something much more dense must be in Earth's interior
obsidian
volcanic glass
Sahara dust (dry air)
weaken a strong hurricane and prevent a tropical wave from strengthening - Less moisture - Dust reflects light, so ocean temp. is cooler
streak
what does the powdered form look like
hardness
what minerals can scratch it or be scratched by it Scale: 1-10 (soft --> hard)
The Earth is divided into several layers
which have distinct chemical and seismic properties