Curent - North Penn School District / Overvie · Web viewThe rift that split Gondwana and formed...

Marine Science Unit 1 Section 1:Geology of the Oceans

A) How did the oceans form?1) Earths surface first started accumulating water about 4

billion years ago, however there acre currently 2 leading theories that state how this could have happeneda) Volcanic cycling theory – the theory which states that

all of earths water was released by volcanic emissions(I) When volcanoes on early earth erupted they put

lots of water vapor into the air(II) Once earth cooled this water vapor condensed,

formed rain, and the deepest point of the earth filled with water

b) Comet theory - the theory which states that all of earth’s water comes from earth colliding with comets and other celestial bodies which contain ice (I) Some scientists sight data which suggests that earth

is constantly being bombarded by comet like balls of ice that vaporize once they enter earths atmosphere

(II) They believe that it is these alien ice balls that first delivered all the water to earth.

c) It is most not one or the other but both

The 4 oceans:The pacific ocean (largest and deepest)

The Atlantic OceanThe Indian Ocean

The Arctic ocean (smallest and shallowest)

B) The origins of the oceans and seas1) 200 million years ago

a) Pangea – the original continent on earth which consisted of all the continents joined together

b) Panathalassa- the one singe ocean which surrounded pangea and the planet. This was the ancestor of the pacific ocean

c) Sinus Borealis – an indentation in the northern coast of pangea that would become the artic ocean

2) 180 million years agoa) 180 million years ago a rift started to form

between north America and Europe which were joined together. (I) This rift split Pangea into two smaller

contents, Laurasia and Gondwana(II) The rift was called the mid Atlantic ridge

and would eventually from the Atlantic ocean

Marine Science Unit 1: Geology of the Oceans Of 9

The Volcanic cycling theory states that all of earths water was released by volcanic emissions

Earth 200 million years ago


(i) Laurasia- prehistoric super continent that was composed of north America, Europe, and Asia (ii) Gondwana- prehistoric super continent that was composed of South America, Africa, Antarctica,

India, and Australia

3) 150 million years agoa) A new rift forms in Gondwana splitting up b) Africa and Antarctica.c) This rift would form the Indian ocean

4) Todaya) The Atlantic ocean is still growing while the

Panathalassa (the pacific ocean) is still shrinking

b) The rift that split Gondwana and formed the Indian ocean extended to create the red sea which is actually a young ocean

C) Alfred Wegner and plate tectonics1) Alfred Wegener – a German geophysics who first formerly proposed the idea of continental drift

a) Alfred Wegener compiled multiple peaces of evidence which suggested that the earth was once together in one super continent called pangea (Latin for all land)

2) Wegner called his theory Plate Tectonics a) Plate tectonics – the theory that the continents where once together as one unified land mass but they have

broken apart and are still moving b) The problem with Wagner’s theory was that he could not provide evidence for a force strong enough to

move continents, and so he was largely ignored by the scientific community

D) Henry Hess and Sea Floor Spreading1) In World war II, Henry Hess, a US Navy captain in world war II mapped the Atlantic sea floor using a depth

recorder looking for German subs2) Hess discovered a huge mountain range in the middle of the ocean with a deep valley between it. He called the

mountain range the Mid Atlantic Ridgea) Mid Atlantic Ridge – spreading centers where new sea floor is being created



Second peace of Wagner’s evidence:Manny continents like Africa and south America seem to fit into each other like a jigsaw puzzle

First peace of Wegner’s evidence:Fossil evidence shows many continuous lines of fossils

that seem to cross oceans

(I) Hess took this discovery and published a paper in 1960 saying that the ridge is formed as magma rises up through these deep valleys and forms new ocean floor

(II) This constant creation of new ocean floor forces the two oceanic plates that meet at the ridge to move apart or spread

(III) Hess called this idea Sea floor spreading(i) Sea floor spreading – Henry Hess’ Idea that the old sea floor moves away from the ridge in order to

create room for new sea floor (ii) Thanks to Hess’ idea of sea floor spreading there was finally a force large enough to support

Wegner’s idea of plait tectonics

E) Evidence for sea floor spreading1) In the past 60 years Scientists have studied ocean floor near the ridge1) These studies have found that bands of rock closest to

the ridge had large quantities of iron that gives that rock unique magnetic propertiesa) Depending on when the bands of rock hardened the

iron particles point north or southb) Scientists use the direction the iron particles are

pointing to tell the difference between newer rock formed near the ridge and older rock

c) Because over time scientists have observed older bands moving away from the ride and newer bands of rock forming closer to the ridge they concluded that the sea floor is spreading

B) What happens when plates meet1) The earths crust is mostly made out of two main types

of rock, oceanic basalt, and continental granitea) Basalt – the dense rock witch rises up through the

ocean ridges and makes the ocean floorb) Granite – the less dense rock that composes most

of the continents(I) Because ocean basalt is more dense than continental granite, when these two rocks meet at plate

boundaries, the ocean plait usually sinks under the continental plate and melts

Ocean basalt is denser than continental granite, so when these two rocks meet the ocean basalt usually sinks under the continental granite. This process of sinking is called Subduction

(II) Subduction – the process of one tectonic plate sinking under the other and melting(i) Because Subduction involves the melting away of one plate it creates room for new ocean floor to

form at the ridge(ii) Subduction causes trenches to form on the ocean floor

Trench – a deep depression in the ocean floor caused by one plate sinking under another as they meet


Scientists use the direction the iron particles are pointing in ocean rock to tell the difference

between newer rock formed near the ridge and older rock

The Marianas Trench in the pacific ocean is the deepest trench in the world as well as the deepest point in all earths oceans

C) The importance of ocean trenches1) Manny different land formations are formed as a result of an oceanic trench2) What type of land formations form depends on what types of rock meet

When Basalt meets Granite rock:1) When oceanic basalt meets continental granite the

more dense basalt subducts under the less dense granite creating a trench and melts.

2) This hot melted basalt rises under the continental plate and create mountain ranges like the Andes

When Basalt meets Basalt:1) When oceanic basalt meets oceanic basalt, one

plate subducts under another creating a trench, and starts to melt

2) This hot melted basalt rises under the other oceanic plate and creates large volcanic islands arks like the Aleutian islands

Marine Science Unit 1 Section 2:Ocean Provinces

A) Two main regions of the ocean1) The ocean floor is divided into two main regions or provinces, the relatively shallow continental margin and the

deep ocean basin2) Because plate tectonics creates all the features in these regions the same main geological features mark each

regiona) The continental margin – the shallowest parts of the ocean that consist of the area between the continent

and the deep sea floor(I) The continental margin has 3 main features, the Continental shelf, the Continental slope, and the

Continental rise.b) The deep ocean basin– the deepest parts of the ocean that consist only of oceanic basalt

(I) The main feature on the deep ocean floor is the abyssal plain, however there are occasional mountains called seamounts and guyots

(II) The deep ocean basin comprises about 30% of the surface of earth


The ocean floor is divided into two main regions, the relatively shallow continental margin and the deep ocean basin

B) Features of the deep ocean basin1) Most of the deep sea floor lies at a depth of about 13000 ft under water2) the majority of the deep sea floor is flat and is called the abyssal plain

a) The abyssal plain – the flat region of the deep sea floor(I) the abyssal plan is dotted with submarine volcanoes that are in various stages of life

b) Trench – a deep depression in the ocean floor caused by one plate sinking under another as they meetc) Ridge – spreading centers where new sea floor is being created

Marine Science Unit 1 Section 3:The movement of ocean water

A) The two directional movement of ocean water1) Ocean water moves in two main directions in the ocean, horizontally across the surface of the water, and

vertically from the depths of water into the shallows

B) Currents move water horizontally1) Current – the name given to the horizontal

movement of water across the oceans surfacea) All currents are driven by wind blowing across

the ocean(I) As wind pushes water, the current moves

away from the direction of the wind at an angle of 45o, this creates a swirling motion

b) Currents in the ocean act mainly to regulate the oceans temperature, moving warm water from the equator to the poles and moving cool water from the pools to the equator

C) The great ocean conveyer (Vertical circulation of water)

a) Upwelling – the upward movement of water from the deep water to shallow water(I) Upwelling results from because warmer less

salty water in the deep rising because it is less dense

(II) Upwelling is responsible for delivering nutrient rich water from the deep into the shallows at the equator


b) Downwelling – the downward movement of water from the surface to the depths (I) Downwelling results mostly from colder more salty surface waters sinking because it is more dense (II) Downwelling delivers oxygen rich water to the depths at the pole

D) Anatomy of a wave 1) Although waves are constantly moving

they have defined measurable featuresa) Crest – the highest part of the waveb) Trough – the lowest part of the wavec) Wave height– the vertical distance

between crest and troughd) Wave length – The distance between

two wave crests

E) How to make a wave1) Most waves seen in the ocean are created by wind2) The size of a wave depends on two things:

a) The stronger the wind the bigger the waveb) The longer distance and period of time the wave blows over the bigger the w

F) What happens when ocean waves get to shore1) Surf zone – the border between the ocean and shore where wave swells release there energy in the form of

breakers2) There are 4 steps to how a wave breaks:

a) As the wave enters the surf zone the bottom of the wave begins to rub against the bottom of the oceanb) The more the bottom rubs, the more the wave slows downc) As the wave begins to slow its starts to squish its sides together and the wave height becomes larger as the

wave length becomes shorterd) Eventually the wave height becomes too high to be supported by the base and the wave topples over

As a wave enters into the surf zone it begins to slow down. As the wave slows, the height of the wave builds and the length of the wave shortens. Finally the wave becomes unstable and topples over on itself

G) Wave types1) What type of wave breaks depends on the characteristics of the shore bottom2) There are two basic types of waves, plunging breakers and spilling breakers


Plunging breakers form on steep sloping surf zones:Plunging breakers – waves the have a curling crest that move over a air pocket or “pipe line”

a) The steep sloping surf zone causes the bottom of the wave to slow down a lot faster than the top.

b) This type of slowing causes the whole wave to lean towards the shore and the top to fall over on the wave

c) Plunging breakers don’t have to be large, in fact:

WAVE SIZE HAS NOTHING TO DO WITH WAVE TYPE

Spilling breakers form on gentle sloping surf zones:Spilling breakers – waves that have a turbulent mixture of air and water at the crest

a) the gentle sloping surf zone only slows the wave a small amount

b) this type of slowing causes the top of the wave to spill over on itself

c) Spilling breakers don’t have to be small in fact:

WAVE SIZE HAS NOTHING TO DO WITH WAVE TYPE

D) Rogue waves1) In the open ocean waves are

constantly passing through each othera) When waves pass

through each other they can either combine their energy to briefly make a larger wave or impede there energy and briefly make a smaller wave(I) Wave construction –

when two waves meet crest aligning with crest there heights add to make a wave that is much higher(i) 1:23 waves will encounter wave construction and be twice the average height(ii) 1:300,000 will be 4 times the height(iii) the chance of a truly monstrous wave is about 1 in a billon but it does happen

b) Rogue wave – massive weaves that can reach more than 100 ft higher in height than the surrounding surf resulting from constructive interference in the ocean


When waves pass through each other sometimes there crests perfectly align and the result is a wave that is briefly much higher. Rogue waves can result from multiple waves randomly coming together in this way

E) Tsunamis1) Tsunami – a large wave created by tectonic activity within the earth

a) There are a few causes of tsunamis:(I) The quick upward movement of the earths crust in a earthquake displacing water on the oceans surface

can cause a tsunami(i) This is the most common cause of tsunami however this produce the smallest waves

(II) Avalanches, mudslides, and Meteorites plunging into water canm also cause tsunamis(i) The latter two are much less common but have been responsible for the production of the largest

waves to have ever occurred in the oceanb) In open water the height of a tsunami is only about a meter or so but it can be moving faster than the speed

of sound. For this reason tsunamis are only observable once they reach the shore

F) How the sun and moon create the tides1) Tides – the rise and fall of water level on earth resulting from the gravitational pull of the moon and sun on the

earth 2) The moon and suns gravity pull on all parts of the earth

a) The moon pulls more than the sun because it is closer3) Because land cant go anywhere, only the earths water responds to the gravitational pull of the moon and the

suna) Tidal bulge – a large swell of water that results from the gravitational pull by the sun and moon and earth.

(I) The first tidal bulge forms as water is pulled towards the moon from the sides of the earth (II) The second tidal bulge forms because the water from the sides of the earth cant all fit on the side of

facing the moon, so some of it drains to the exact opposite side(III) These two tidal bulges caused by the moon create the high tide and low tide points on earth

b) High tide is always directly below and opposite where the moon is around earthc) Low tide is always on the side of earth the moon is not

G) Types of Tides1) Spring tides – when the sun earth and moon align (full moon or new moon) causing a large difference between

high and low tidea) The pull of the sun and moon work together in spring tidesb) Spring tides result from New and full moons

2) Neap tides – when the sun earth and moon form right angles to each other (half moon) causing very little difference between high and low tidesa) The pull of the sun and moon cancel each other out in neap tidesb) Neap tides result from Quarter or half moons


EarthMoon

Steps to determine what tide is where on earth:1. First determine High and Low tide:

a. High is directly below and opposite the moonb. Low tide is always to the right and left of the moon

2. Second determine Spring or Neap tide:a. Spring tide occurs when the earth sun and moon align (full and new moon)b. Neap occurs when the sun earth and moon form a right angle (quarter moons)


Curent - North Penn School District / Overvie · Web viewThe rift that split Gondwana and formed...

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