Bathymetry

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Bathymetry

• Oceanography Lab 1
• Prof. Rodriguez

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• bathymetry (bathymetric) from the Greek root
  bathy meaning depth, and metry meaning
  measurement.
• Sounding depth measurements
• isometric - lines of equal measure
• contour lines - lines of equal height
• isobath - lines of equal depth

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• Echo sounder or fathometer produces sound and
  is used to measure depth
• Sound in sea water travels
• about 1450 meters/second
• We can calculated the depth if we know the time
  it takes sound to travel

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• The deepest part of the ocean, the Marianas
  Trench, compared with the highest point of land,
  Mt. Everest is approximately 5.5 miles (29,000
  feet) high, and the Marianas Trench is
  approximately 7.4 miles (39,000 feet) deep.
• This means we could set Mt. Everest in the
  Marianas Trench and still have almost two miles
  (10,000 feet) of ocean water between its highest
  point and the ocean's surface.

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• Topographic maps are basically a bird's eye view
  of a region of land in which elevations are
  expressed with labeled contour lines.
• The path of the lines follow the contours of the
  slopes they represent.

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• Such drawings of the land are known as maps, but
  if the drawings are of the sea floor, they are
  known as charts.
• The 805 meters would be the highest point on
  land, but it would be the lowest point in the
  sea. If a straight line is drawn horizontally
  across the map above such that two of its points
  cross the two highest elevations, the profile of
  the land along that line looks approximately like
  this

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• If those two points are considered depth because
  the drawing is a chart of the sea floor, the
  profile would be a mirror image

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Rules of Construction of Bathymetric Chart

• 1. Isobaths never cross one another
• 2. When isobaths go thru a canyon or a deep
  valley, they have a V-shape with the apex of the
  V pointing toward shallower water.
• 3. An isobath must separate depth zones
  completely
• 4. Close spacing indicates a steep slope, widely
  separated a gentle slope
• 5. An isobath or contour line closes upon itself.