Todays Tune - PowerPoint PPT Presentation

About This Presentation
Title:

Todays Tune

Description:

Spring tides occur when the Earth, Sun, and Moon are aligned. New Moon and Full Moon phases ... Searching for food. Movie Trivia. Jeopardy, 1953, Barbara ... – PowerPoint PPT presentation

Number of Views:58
Avg rating:3.0/5.0
Slides: 30
Provided by: duskGe
Learn more at: http://dusk.geo.orst.edu
Category:
Tags: moon | movie | new | todays | tune

less

Transcript and Presenter's Notes

Title: Todays Tune


1
Todays Tune
  • Aqueous Transmission
  • Incubus

2
Chapter 8Tides
3
Tidal Characteristics
  • single waves - stretch across entire ocean
    basins.
  • shallow-water waves
  • wavelengths greatly exceed the depth of the
    ocean.
  • complex interactions of moon and sun

4
Origin of the Tides
  • Unlike wind-driven surface waves and unlike
    tsunamis, tides are caused by two principal
    factors
  • Gravitational attraction
  • Centrifugal force

5
Gravitational Attraction
  • All masses are drawn to each other.
  • The moon because of its closeness to the Earth
    exerts a greater gravitational effect on the
    Earth than the Sun, despite the fact that the Sun
    is much more massive than the Moon.

6
Gravitational Effect of Moon(Figure 8-5a)
7
Animation courtesy of NASA Goddard Space Flight
Center The Moon's gravity tugs at the Earth,
causing ocean water to slosh back and forth in
predictable waves called tides. We can visibly
observe some of that energy dissipate at the
beach, with waves rolling across coastal shallows
and shoals. Most of the energy dissipates due to
friction between the water and the shallow floor
beneath it
8
Centrifugal Force
  • Earth and Moon revolving around one another.
  • unequal masses of Earth and Moon
  • center of rotation lies beneath the Earths
    surface.
  • second tidal bulge
  • ocean shifts away from center of rotation

9
Centrifugal Forces Center of Rotation(Figure
8-5b)
10
2 Bulges from Gravitational Attraction
Centrifugal Force(Figure 8-5c)
11
Animation
12
Dynamic Model of the Tides(Figure 8-8a)
13
True Tidal Waves (not tsunamis!)
  • The motion of water around the basin is a rotary
    wave.
  • The crest is at one side of the basin.
  • The trough is at the other side of the basin.
  • Tides have characteristics of both progressive
    and standing waves.

14
Standing Waves
  • Sea, swell, and surf are progressive waves.
  • Standing waves (seiches)
  • Oscillate back and forth about a node, i.e., a
    fixed point.

15
Node Fixed Point Antinode maximum
displacement(Figure 7-11)
16
Dynamic Model of theTides(Figure 8-8a)
17
Dynamic Model of theTides(Figure 8-8b)
Earth rotates from W to E Tidal bulge to W
Pressure Gradient Coriolis
cut-away
Pressure Gradient Coriolis
Pressure Gradient Coriolis
cut-away
18
Dynamic Model
  • equilibrium model of the tides is good, BUT...
  • not totally detailed and accurate
  • oceans are separated by continents
  • oceans not infinitely deep

19
Animation courtesy of NASA Goddard Space Flight
Center Using 6 years of data from TOPEX/Poseidon
satellite altimeter, they derived a 16-day set of
predictive data, showing a synthetic view of how
the tides move around the world's oceans.
20
Key Features of Tides
  • High tide Wave crest
  • Low tide Wave trough
  • Tidal range Wave height
  • Tidal periods depending on location
  • 12 hours, 25 minutes
  • 24 hours, 30 minutes

21
Wave Parameters(Figure 7-1a)
22
Tidal Periods
  • why not exactly 24 hours or 12 hours?
  • Moon moves forward in its orbit each day.
  • Takes 50 additional minutes for a spot on the
    Earths surface to regain its position relative
    to the Moon.

23
Classification by Daily Record
  • Diurnal have one high tide and one low tide
    daily (high lat).
  • Semidiurnal have two high tides and two low
    tides daily (low lat).
  • Mixed there are two high tides and two low tides
    daily, but of unequal shape (mid lat).

24
Classificaton by Monthly Record
  • Spring tide phase when tidal range is maximal.
  • Neap tide phase when tidal range is minimal.
  • There are 2 spring and 2 neap tides each month

25
Spring Neap Tides
  • Spring tides occur when the Earth, Sun, and Moon
    are aligned.
  • New Moon and Full Moon phases
  • Constructive interference
  • Neap tides occur when the Sun and Moon are
    aligned at right angles to one another.
  • Quarter Moon phases
  • Destructive interference

26
Sun/Moon/Earth - Spring Neap(Figure 8-7a)
27
Marine Biorhythms
  • Cyclical behaviors associated with tidal rhythms.
  • The diurnal activity of fiddler crabs.
  • The spawning behavior of the grunion fish.

28
Diurnal Activity of Fiddler Crabs(Figure B8-4)
Natural
Searching for food
in burrows
29
Movie TriviaJeopardy, 1953, Barbara Stanwyck
Write a Comment
User Comments (0)
About PowerShow.com