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