Metal Detecting High and Low Tides
by Lee Wiese
The definition of tides from Wikipedia
Tides are the rise and fall of sea levels caused by the combined
effects of the gravitational forces exerted by the moon, sun and the
rotation of the earth.
One of the questions one must ask is:
are the key causes and why are there tide variations from day to day?
Generally there are four different tide changes for each 24 hour day of the
month: High Tide, Low Tide, High Tide, Low Tide with each tide change being
approximately six hours apart. This is the usual tide pattern for any given
24 period, however, for some locations there may only be one high and low
tide each day.
The contributing factors for tide change are the centrifugal forces of the
earth and moon rotation around each other and the gravitation forces of the
moon and sun on the earth. Also the forces can be greater or lesser
depending the distance of the earth from the sun and moon. For a much more
detailed scientific analysis of tide actions go to the following website:
Our Restless Tides
This site provides a brief explanation of the basic factors
which produce tides.
There are five short chapters with diagrams and a
explanation of the effects that time, distance, moon, sun and the earth's
rotation has on coastal tides. Good site.
The best way for a detectorist to gain real time tide knowledge for their
area is to acquire a set of tide tables for the salt water beach areas that
are of interest. Most tide tables will provide the detectorist with all of
the information required to having a greater chance of detecting valuable
How to read tidal information?
To the left is a typical tide table found on the web. Usually it will
display the city name, in some cases a GPS co-ordinance, date, time (24 hour
clock), time zone, the high and low tides for each 24 hour period with
sunrise & sunset times.
The high and low tides are recorder in feet from relative mean sea level
which is a zero level. A low tide may exhibit a negative number (i.e.: -0.9
feet) this will be the lowest point of the tide and will occur at a specific
time (i.e.: 14.59 PST in the table) this tide is negative or minus relative
to mean sea level. High tides are recorder in feet with a positive number so
at 08:08 PST the tide is +5.87 feet above relative mean sea level.
The graph on the left represents the table data overlaid on a 24 hour clock
period that is placed on the graphic bottom (x-axis) on the left side
(y-axis) is the measurement in feet (ft). The graph displays the four tides
during a 24 hour period for a beach. Generally the best metal detecting
takes place at the 24 hour period lowest tide.
Also note that one low tide is +2.44 ft and the other low tide is -0.9 ft
and the high tides are also not equal with the highest tide at +5.87 ft and
the other high tide at +4.45 ft. This is the result of the gravitational
forces and the distances of the moon from the earth in the 24 hour period
plus other factors.
Take a few minutes to compare the two tide charts in this article. The first
item to note is that they appear slightly different during the 24
period. The dates on the charts are three days apart and the 02-16 first low
tide is at 02:07 am, in the second chart on 02-19 the first low tide to
04:30 am. The low tide has moved in time 2 1/2 hours in three days. Plus the
second low tide on 02-19 a -.29 ft low tide. So time is a critical element
in reading tidal information.
There are also changes to the other tides from the 02-19 chart as compared
to the 02-16 chart. This is why it is necessary to acquire a tide chart
booklet or tide tables before doing any salt water beach detecting. Tidal
changes take place each day of the month and at certain times of the month
there are extreme low tides which contribute to greater beach sand exposure
and shallower shore line waters.
Where to get tide information?
usually purchase annual tide booklets in or near the area that you plan to
metal detect or you can go online and select one of the web site URLS below
and get tidal information for most of the coastal regions in the U.S.
NOAA Tide Predictions
Regions with Tide Predictions
WWW Tide and Current Predictor
Why is it necessary to consider tidal information
for salt water beach metal detecting?
Another effect on tide change is the distance your beach area is from the
equator. The greater the distance from the equator the greater the tide
change between high and low tide.
Tide Change Examples.
Alaska +13 ft to -1.5 ft
North CA +6 ft to -1.6 ft
Florida +3.5 ft to -.4 ft
Mass. +11 ft to -1.8 ft
Finally there are only a few good days in the month to metal detect low
tides so it is essential to keep reviewing tide tables to find the best days
for each month. The understanding and knowledge of tide times, tide heights
and tide lows can be very important to any salt water beach detectorist.
This knowledge can contribute to a greater chance of detecting interesting
and valuable finds while at the beach.
There are basically three sections
to any beach: dry sand, wet sand and sand under the water. This article will
not address the dry sand portion of the beach since the article is primarily
focused on the tidal area of the beach. The tides have the greatest effect
on the wet sand and beach sand under the water. Tide changes either increase
the water level depth at the shore line or reduce the water level depth at
the shore line. Tide changes can also expose more beach sand.
There are some benefits to
detectorist from high tides. Probably the most important benefit is that if
the high tide takes place during the recreational daytime, people are
swimming, playing water tag, etc,. This puts beach goers that are in the
water closer to the shore line because of the additional water depth. This
is important to note since at low tide the beach area that was under water
at high tide may now be wet sand at the extreme low tide (minus tide). Thus
detecting the wet sand can be very productive for valuable finds that may
have been lost during high tide water activities. Also high tides can erode
sand from the beach crest and blanket area. This erosion can pull lost
coins, jewelry and other items from the beach crest sand and place the lost
items on the wet sand slope of the beach which now can be recovered by the
detectorist at low tide without going into the water.
The low tide area has many
positive attributes for the detectorist. The detectorist should always be
looking for the extreme low tides which are usually a minus tide (-1.5 ft or
greater) if you are in the northern portion of the U.S.
1) The low tide exposes sand that was previously under water at the high
tide. This is important in a couple ways. The detectorist does not have to
be water detectorist to get at item lost in the water since the low tide
exposes much of the high tides water portion of the beach now as wet sand.
If you are a water detectorist the low tide makes its much easier to detect
further out into the salt water beach area since the water depth has
2) The low tide sand area is where most of the beach activity takes place.
So this is where you will probably find most of the lost jewelry. Also the
low tide will expose the following beach characteristics: more of the beach
slope, cuts created by a high tide, scallops on the slope, troughs, ripple
cuts, flat spots, rock, pebble and shell areas, etc.
Another interesting beach characteristic is the wet line mark on the beach
slope at low tide. This wet line mark is usually the result of the high
tide. This mark represents where the high tide hit the beach and broke
apart. It can be beneficial to metal detect this area. This wet line mark
will run parallel to the beach crest and shore line. Each of these beach
characteristics can provide different age factor finds. How to detect each
of these different beach characteristics is a discussion for another
You will also find a lot of information on beach characteristics in:
Overview of Metal Detecting Saltwater Beaches
on the MDHTALK
3) Low tides allow the water detectorist to go further out into the salt
water beach area. Many people
swim and play water activities in very deep water. Low tides reduce water
depth thus providing the opportunity to detect this area with simpler water
So when should a detectorist hit the beach to
. The suggestion is to start
detecting a low tide if it is either a zero (+ - 0 ft) or minus tide two
hour before and after the low tide mark for a total of three - four hours.
This is detecting the tide as it moves down the beach slope and detecting
the tide as it moves backup the beach slope towards the high tide mark.
The suggest for a detecting a high
tide is to detect the area below the high tide crest two - three hours
before the crest of the high tide. The area to detect is the wet sand on the
beach slope just below the high tide mark. This can be productive if the
previous high tide did any erosion of the beach crest.
Other actions that can influence tides
Storm surges caused by hurricanes and other major storms can cause high
tides to be much greater in strength and therefore cause a good deal of
beach erosion providing that these surges occur in conjunction with the high
High on shore winds can also contribute to greater high tide crest resulting
in beach erosion.
1) Read the beach for the best place to start your detecting experience.
2) Always dig all targets at the beach.
3) Listen for those faint target sounds.
4) Slow down and keep your coil level and on the sand.
5) Respect other beach goers.
6) Keep you distance from beach goers that are enjoying the beach sand.
7) Remove all trash dug.
8) Fill all holes dug.
9) Have fun.
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