Absolute dating
Whenever it is possible to date an artefact or a site to a particular year (or interval of
years). This can be made using dendrochronology, carbon-14, or datable objects such as coins.
AIMA
Australian Institute of Maritime Archaeology
Aircraft
There are plenty of sunken aircraft underwater, many of them from World
War Two. Some are just fragments, but others are intact. This area is
researched by Steven Carmichael-Timson and Adam Wilson at Sea-Tech
Exploration, UK.
 Airlift
A wide tube is lowered to the excavation site. Into the lower end of the tube compressed air is
pumped from the surface. The air bubbles up and creates a suction. This pulls up water, sand, and
small objects. All of this can be sifted on deck. Photo at right by Mary Rose Trust. Detail
photo.
Air survey
This search method was used already in the 1930s to search for old ports at the coast off
Lebanon. It has also been used in Switzerland and Florida. In the 1990s, the north German coast has
been surveyed by a small plane from 150-600 m altitude. Several wrecks were found, photographed and
positioned by GPS. Except from shipwrecks, submerged settlements and other structures can be found.
This method is suitable for coastal areas with a shallow and flat sand bottom. Thus it works for
the south Baltic Sea (flat sand bottom) but not in the north Baltic Sea (rock or clay bottom).
Successful work requires bright sunlight over a calm sea with clear water. (Ref. otto.braasch@landshut.org)
More info.
Large round ceramic container used for transportation and storage of goods. Used from antiquity
until the 16th century or so. Used for wine, oil, olives, grain, etc,
etc. Amphoras in a shipwreck can often tell the age and nationality of the
wreck. More info.
Analysis of a find usually involves classification and dating.
This is a basis for interpretation.
Archaeology
Knowledge of human life through the study of human antiquities, especially of the prehistoric
period (no written sources) and usually by excavation. However, underwater archaeology also
includes the historic period (written sources).
The physical setting, location, and cultural association of artefacts and features within an
archaeological site. Artefacts removed from their context lose a lot of their information. See
Context.
Artefact / Artifact
Any object made or modified by humans.
Astrolabe
Instrument used for celestial navigation. A large collection (more than 10) is displayed at the
Museu de Marinha in Lisbon. Photo of astrolabe from the Batavia, courtesy Western Australia
Maritime Museum. Illustration of usage.
AUV
Autonomous Underwater Vehicles are underwater robots that are not
remote controlled and operate with artificial intelligence. Just like ROVs
they are used instead of divers for difficult operations,
e.g. on great depth. More info.
Avocationals
These are recreational scuba divers and amateur underwater archaeology groups who give
invaluable help to underwater archaeologists. Examples are volunteer unpaid divers during
investigations and diving clubs cooperating with archaeologists and maritime museums.
The world's largest brackish water sea,
located in northern Europe. The low salinity affects not only teredo
navalis and shipwrecks, but also all animal life, where the fish are
of different species. The oceans have a salinity exceeding 3%, but the
Baltic Sea has a salinity of 0.8% in the south, 0.3% in the north and 0.6%
in average. Through currents there is a constant exchange of salt water
from the Atlantic with brackish water from the Baltic. The heavier salt
water stays in the deep, usually below 40 m depth (in the south) and 80 m
depth (in the north). The lighter brackish water is always nearer surface.
Between these layers there is also a constant exchange with the water
movements – salt spreading up, and brackish water and oxygen diffusing
down. For reasons unknown, perhaps climatic change, the Baltic Sea
salinity is reducing, and several fish are now endangered.
Common ceramic in the 17th and 18th centuries. May have contained wine or beer. Drawing of a jug
from the Vergulde Draeck (1656) drawn by Jeremy Green, courtesy Western Australia Maritime
Museum.
A boat grave is a kind of ship burial, where a small boat is used.
Examples of boat graves are Neolithic log boat graves, like the St
Albans logboat grave. Other examples are planked boats used in Viking
Age burials, perhaps they were simply poor man's/woman's versions of the
larger ship burials.
Mixture of seawater and freshwater. The low salt-rate usually excludes those organisms that eat
wood on shipwrecks, e.g. the shipworm Teredo Navalis. Read more
about the Baltic Sea.
Bronze
Alloy composed of 90% copper and 10% tin. Highly resistant to corrosion
but not as strong as iron or steel.
Bronze Age
The era when bronze was first used but not yet iron. In Minor Asia and the Mediterranean it was
from c 3300 BC until 1200 BC. But in the Nordic/Scandinavian area it was from c 1500 BC until 500
BC.
Cannon
Cannon finds can identify a shipwreck, but not always. Bronze guns were often taken in battle
and reused on new ships. Sometimes the guns could be 100 years old already at the time of sinking. More
info.
Natural waterfilled holes on the Yucatan peninsula, Mexico. Used as ritual wells. Many of then
contain artefacts sacrificed to the Mayan gods. The cenotes are now being investigated.
The cenote at the sacred city Chichen Itzá in Yucatan, Mexico, has been
investigated since the 1960s.
Ceramics
See pottery.
Children
See kids.
Created by John Harrison, the father of modern navigation. The chronometer is a clock that is
accurate enough to calculate the longitude of a ship's position. In 1763 he built such a clock and
was later awarded a £20,000 prize for his invention. Link.
As well as the line and square search patterns, this is a simple method for divers to search an
area of the seabottom. The diver starts at a fixed point on the bottom. Fastens the search line.
Swims a circle with the line stretched. For each turn this line must be slackened.
Clay pipes
These tobacco pipes were popular during the 17-19th centuries. They were fragile and had a short
life span. Thus they are a good aid in dating maritime finds. More info.
Can commercial interests and archaeology co-exist? The answer depends on whom you ask. See Ethics,
Economy, Selling artefacts, Debate,
and Salvage.
Stone-like encrusted clump/conglomerate created by the natural elements around an artefact,
often rusted iron. If a concretion around an iron object is cracked underwater, black
"smoke" pours out. This is not good, because without the protective concretion, the
remaining iron is exposed to further rusting. Concretions should never be cracked, just documented.
If a decision is made to recover, the entire concretion should be recovered and quickly be placed
in a jar of sweetwater, pending further investigation, possibly by X-ray. A concretion sometimes
contains the hollow space after an object that has rusted away. Thus it’s important not to crack
it. Such a hollow can be casted by filling it with epoxy, saving the object’s original form.
Having received an object, the conservator's task usually includes cleaning, documentation and
analysis, and finally, stabilisation. Wood and organic material can be stabilised using
freeze-drying or PEG. Metal can sometimes be treated with electrolysis.
More
info.
The careful investigation of objects in situ usually gives far more valuable information,
than just the object by itself. An object without provenance (place of origin) has lost its story.
Used underwater on wooden ships to repel marine organisms. Compare with
lead sheathing. Copper sheathing was first
used by the British Royal Navy in 1761. In 1832, George F. Muntz developed a
cheaper, more durable alloy of copper and zinc (59-61% copper, 38-40%
zinc, and 0.5-1% tin). More info.
Except for gold, metals corrode in sea water. Corroded metals are a
special problem. Sometimes iron has disappeared totally, just leaving a
cavity inside a concretion, which can be casted
(filled with plastic or plaster). Sometimes the metal is still there, but
need various conservation treatment. This is
described by Donny Hamilton in Methods
of Conserving Archaaeological Material from Underwater Sites.
Dwellings built on lakes in Ireland and Scotland. They were constructed on
small natural or man-made islands, in lakes, rivers, or swamps. The remains are
often partly
submerged. This submerged environment offers good preservation for organic
material. As an example, in Loch Tay (Scotland), 2500 years old butter has been found. More info.
Cross staff (Jacob's staff)
Instrument used for celestial navigation. This instrument was eventually replaced by the quadrant,
the octant, and the sextant. Photo.
As long as wreck divers do not damage a historically valuable wreck, it should remain available
for everybody. Unfortunately, some valuable wrecks (at least here in Sweden) have been damaged,
resulting in all diving prohibited on those sites. Pity. Cultural tourism with minimal impact
should be ideal for everybody. See Look but don't touch.
Decay
This is also called site formation. In most oceans (except the Baltic Sea and a few other
places), a shipwreck under water deteriorates rapidly during a first stage. This often takes
decades for a wooden ship and about a century for a steel ship (shorter time in shallow water).
What remains after that is usually stable for millennia if it remains covered by sand, sediment,
coral, or other encrustions. A relatively stable wrecksite is usually in no urgent need of
excavation, except for the risk of being destroyed by unexpected natural causes or human impact.
More on degradation.
Degradation
See Decay.
 Dendrochronology (tree-ring dating)
This is a way of dating past events or climatic changes by a comparative study of annual rings (growth
rings) in tree trunks. Depending on annual weather changes, the rings are
thinner or thicker, creating a fingerprint-like pattern. Reference charts
for such patterns have now been created covering more or less the last
couple of thousand years. When compared patterns match, each ring
corresponds to an exact and known year. This way an old a piece of wood
can be dated. To get an exact year from e.g. pieces of a shipwreck, it's
necessary to find a piece that includes "surface wood", closest
to the bark, else the dating will be approximate. More info.
Destructive archaeology
Most investigation methods in archaeology are destructive. We destroy what we study. Thus it’s
important to –
A: Excavate just as much as necessary. A stable site may be better to leave untouched to coming
generations. They will be happy, and perhaps also possess much finer investigation methods.
B: Document the investigation as thorough as possible. Future analysis may need just those tiny
details that may seem insignificant today.
This is described in Archaeology from the Earth by Sir Mortimer Wheeler (Penguin 1954).
Diving bell
Diving bells (dive bells) are described in Italy already in the 1530s.
In the 17th century divers worked in very large bells. In the top was an
air pocket, and below was free workspace towards the wreck. Around 1650
several of the Vasa guns were salvaged by the diver Hans Albreckt von
Treileben. In the 1690s the concept was improved by Edmond Halley, den
English astronomer. And in the 18th century it was further developed by
the Swede Mårten Triewalds. Around that time, air barrels could be submerged to the
diver. Link. Link.
Object not made by humans, but indicating the presence of humans at a site, e.g. bone, shell and
seed. Garbage can be considered ecofact if it is not modified by humans, otherwise the garbage is
considered artefact.
Limited budget and financing is a problem for archaeology. Only a limited number of wrecks or
artefacts can be excavated or taken care of. Meanwhile, legislation is
needed to protect our heritage against uncontrolled treasure hunting and looting.
Educational
See kids and courses.
Fathom
Traditional unit for depth measurement. Equals 1.8 metres or 6 feet.
Excavation and investigation projects are usually quite temporary. So
lots of archaeologists, and amateur avocationals, constantly need to look
for the next dig. If you look for a fieldwork opportunity, you may try
contacting museums, societies,
academic departments, authorities.
Or try Digging
Abroad, Archaeological
Fieldwork Opportunities or DArV. You may also contact the various replica projects
if that's your speciality.
Galvanism
When different metals are in contact with each other, one "eats" the other according
to the scheme below, listing the most durable metal last. The table also reflects the durability of
metals immersed in water. This knowledge is useful for understanding a deteriorated wrecksite, as
well as for treating recovered objects (never mixing metals).
The galvanic series : zinc, iron (cast iron, forged iron, steel), tin, lead, bronze (61-83% copper
and the rest tin), copper, artillery bronze (88% copper, 2% zinc, 10% tin), silver, gold.
Source: IJNA 11.3 (1982) pp 221-231.
GPS
Global Positioning System is a system for navigation by satellite. Navigation satellites
continuously send signals. The receiver calculates the position with high accuracy. Link.
To map and measure a site, and to position individual finds, a large
or smaller grid is often placed over the site. Such a grid can be made of aluminium framing or
other material. Photo.
High energy site
Wreck site with violent sea movement. This could be a shallow water surf zone, e.g. the wreck
site of San Pedro de Alcantara. Along the Florida coast, this
condition is reported as deep as 30 metres, destroying shipwrecks and sometimes moving bottom sand.
IJNA
International Journal of Nautical Archaeology, published by the Nautical Archaeological
Society four times per year.
INA
Institute of Nautical Archaeology, Texas, USA
is an efficient tool for both information and disinformation. Unlike the printed literature and
press, the web has no efficient quality control. In the electronic democracy, anybody can
write anything. So don't believe everything you read on the web. And if something is incorrect
on these pages, please let me know.
Having documented a find (described what you see), the next step in your investigation
is to make an interpretation. Now you determine what this object has been and what it has been used
for. Sometimes the interpretation is a guesswork. Sometimes you test your theories with a reconstruction.
Investigation underwater
An investigation usually follows a certain procedure.
Iron
If iron artefacts are recovered from seawater, they need to be stored as soon as possible in
sweetwater. Old rusted iron exposed to air, starts to disintegrate in 10 minutes.
Iron Age
The era when iron was first used. In Minor Asia and the Mediterranean it was from c 1200 BC
until classical antiquity, ie until c 600-300 BC. But in the Nordic/Scandinavian area it was from c
500 BC until the end of the Viking Age (c 1050 AD). Roughly the Nordic Iron Age ended with the
introduction of Christianity.
Kids & School
Underwater archaeology can indeed be presented for children and at
school. A
beautiful book for the youngest (up to 12 or so) is Au fond des
mers by Daniel Reyss / Jean-Yves Blot (Gallimard Jeunesse / Octavius aventure 1999, ISBN
2-07-052448-5). Hopefully it will be translated to English and other languages.
For the slightly older there seems to be mostly standard literature. Among
magazines, good examples are Dig
and Arkéo. Any other suggestions? Which books would be good introductions at primary or
secondary school level? Or would TV productions, like Discovery, or
perhaps interactive web sites, be "better" than books?
Used underwater on ancient Roman ships to repel marine organisms. This was forgotten during the
middle ages. From the 18th century, wooden ships were again sheathed with lead or copper.
Photo of lead sheathing in situ, from Angra D wreck,
photo by Paulo Monteiro.
Lift bag
Convenient tool for recovering heavy artefacts. The rule is: Don’t be above it (it
accelerates) and don’t be under it (it may drop objects or flip on surface and crash to bottom). Photo.
Look but don't touch
This is what scuba divers/cultural tourists are told regarding
old wrecks. This is also what archaeologists do, unless they must salvage something. So, what's the
problem with bringing up loose objects? That depends on the particular case. On a historically
interesting wreck site I can give these reasons against salvaging artefacts:
- A salvaged artefact loses its context unless carefully documented. The
context carries more valuable information than just the artefact.
- Salvage, conservation and storage must be paid for. Most museums are already overloaded with
stored artefacts.
- Shipwreck parts in a stable environment (e.g. wreck parts covered by
sand, or wooden wrecks in the Baltic Sea) are often best preserved left where they are, and in
most cases they will remain accessible to future research.
- Excavation methods improve all the time, so we should leave some sites untouched for future
archaeologists.
This problem is (so far) greater for land archaeology than for underwater archaeology. Every
day, poor people in poor countries steal artefacts and ruin archaeological sites. Such objects have
lost their precious context and provenance. They are smuggled to richer countries, like Sweden,
where I live, and are sold. Sometimes stolen objects end up in
museums. It is difficult to stop this, but doing nothing at all would be the worst alternative.
Whenever you see a nice object in a museum, or in a private home, why not ask where they got it from.
A proton magnetometer is a search tool detecting iron. More info.
An underwater site can be mapped in various ways. To position a limited number of spots, fixed
datum points may be used for reference. To create a very detailed map a large grid
(e.g. aluminium frames) may be placed over the area. These methods are sometimes combined with a
photo mosaic.
The archaeology of maritime material culture, e.g. related to shipping or settlements, sometimes
underwater, sometimes on land. More info.
 Mortise
and tenon
During Antiquity, this was a common way to fasten hull planks to each other, edge to edge, by
inserting a multitude of plugs into adjoining planks. It was practiced until the end of the Roman
Empire, often together with the shell-first method.
Nautical archaeology
Can be explained as maritime archaeology, specialising in
maritime activities and technology such as ships, boats and other crafts.
Octant
Navigation instrument measuring solar and stellar heights. Photos.
Osteology
Bone analysis. Human bones are an important source of scientific
evidence about the past.
PEG
Short for polyethylene glycol. A conservation method for old
waterlogged wood. Broken down cells are filled with this solution. Thus PEG replaces cellulose that
has deteriorated from the wood. Without this treatment the wood would shrink and crack when dried. More
info. More info.
To make an overall image of a site with limited visibility, a series of closer-range photos is
made, and later assembled. Such photos can be made from e.g. a fixed grid
frame. Example mosaic, from the Gellen wreck,
Germany, made by Klaus Andrews, Hamburg.
Plotter / Video plotter
 This
is a computer monitor that displays the path of the search ship. It gets the position from a
connected GPS receiver. Thanks to GPS with a plotter, you can use side-scan-sonar efficiently.
Ideally, a search pattern may look like this drawing. Search
pattern from Sture Hultquist.
Polyethylene glycol
See PEG.
Popular science
The movie Jurassic Park may have done more than anything else in recent years for
palaeontology. Likewise, underwater archaeology can benefit from being popularised. A boosted
public interest may in the end give more resources for actual research.
Just like in land archaeology, pottery can easily be typologically dated, and is a useful aid to
date a shipwreck. Examples are the amphora, beardman
jug, and terra sigillata.
Procedure in underwater investigation
The procedure is similar to land archaeology. Very simplified it goes like this: 1. Research,
2. Reconnaissance, 3. Planning, 4. Pre-disturbance survey
& mapping, 5. Excavation
& documentation, 6. Conservation, 7. Analysis,
8. Interpretation & reconstruction,
9. Publication, 10. Re-assessment & criticism.
Compare with the San Pedro fieldwork procedures or the NAS
training. More info.
Provenance
Origin, location, arrangement or relationship of an object or a collection of objects.
A report is considered published once it can be referred to in libraries or otherwise (by
author, title, year, ISBN number etc). Usually it is printed on paper as part of an academic
publication, in a book, magazine or newspaper article. Sometimes it's published only on CD-ROM,
which can be referred to just like a book. A report may also be published only on the web (like
several articles on this site). One problem with web publications is that referrals may be
unreliable, since web addresses sometimes change. If you refer to a web article, just the web
address (URL) isn't enough. You should also include the author, the title, and if possible the
publication date.
Purpose
What's the point of archaeology? Why spend resources on all this anyway? Well, perhaps knowing
our past helps us knowing ourselves. Or, as Sir Winston Churchill put it at a speech in Copenhagen
in 1950: "No amount of technical knowledge can replace the comprehension of the humanities
or the study of history and philosophy."
Quarter rudder
A.k.a. side rudder. Ships of antiquity had two side rudders. Nordic ships had one, placed on the
starboard (right) side. During the middle ages all European ships slowly changed to using one stern
rudder. A rare transitional case of both types on one ship is the Les
Sorres X wreck.
Radiocarbon analysis
This dating method is based on the natural decay of the Carbon-14 isotope (written 14C
or C14). This unstable isotope is accumulated during the lifetime of all organisms. When they die,
the C14 decay starts. Thus, the time since death can be measured on samples of organic material,
e.g. wood. A problem is that the natural rate of radiocarbon has not been constant over the
centuries. This error can often be corrected by calibration. The calibrated age is often 5-10%
greater than the uncalibrated age. Explained in Keith Branigan's Archaeology Explained (Duckworth
1973, 1988). More info.
Ram
The bow of ancient warships had a ram, a rostrum, in the waterline. In that way an enemy ship could be rammed
and sunk without having to board and engage in dangerous close combat. The best preserved ram is
the 2.25 m long and 465 kg heavy Athlit ram, found in 1980, displayed at the National Maritime Museum, Haifa,
Israel. Inside the bronze ram some of the ship's wood is still preserved. Similar rams were once
displayed at the Actium Naval
Monument in Nikopolis as well as on Forum Romanum in Rome. Photo courtesy prof. Elisha Linder. Photo
of ram from replica ship Olympias, by J.S. Illsley.
Reburial
Sometimes the best way of conservation is reburial of the site after investigation. Examples are
Fredricus and the Madrague
de Giens wreck.
Relative dating
As opposed to absolute dating, this gives no date, but instead a relative date (earlier/later)
compared with other finds. This can be the case using stratigraphy.
Remote sensing
See magnetometer and side scan sonar.
Maritime archaeology, specialising in the study of artefacts of early river traffic, such finds
may often consist of e.g. ancient barrages (pole palisades) or logboats.
Example from historic times: Ice Boats of the Leeds and
Liverpool Canal, by Albert Fischer. Another example is the Excavations
in Saône River, France.
Rock art
 Nordic/Scandinavian
Bronze Age rock carvings often depict boats or ships. What those boats looked like in reality
nobody knows. Apparently they had oars but not sails. Perhaps they were similar to the Hjortspring
boat. Link.
ROV
Remote Operated Vehicles are remote controlled underwater robots used instead of divers for difficult operations,
e.g. on great depth. More info.
Salvage
Commercial salvage of objects from relatively young shipwrecks, e.g. Titanic,
may be justified by the fact that the ship is deteriorating, i.e. the wrecksite is not yet stable.
Reasons against salvaging old wrecksites are that they are often stable (thus no hurry) and they
are often historically or archaeologically valuable (information may be lost).
More
info on Salvage and Recovery.
Sea-level changes
See Land rise or Submerged
structures.
Short for Self-Contained Underwater Breathing Apparatus, the most
common and inexpensive diving system. The diver
usually breathes compressed air from one or two tanks carried on the back.
Scuba divers are useful down to ca 40 m depth for e.g. searching,
investigation, documentation and recovery/salvage.
Scupper
A hole built into the base of a ship's gunwale that allows water to
drain off the deck.
Search pattern
During scuba diving, see circular search
– using GPS, see plotter.
Selling artefacts
Artefacts are often sold on the open market, sometimes from over-stocked museums (not considered
ethically acceptable at museums in many countries), and sometimes by private collectors and diving
trophy hunters. This might be viewed as non-problematic as long as excavation and documentation
have been properly carried out. However, it is not ethically acceptable to plan an excavation with
the aim of selling salvaged items and making a profit. A pure profit motive often compromises
excavation and documentation. See Ethics.
A sewn boat is tied together rather than using pegs, nails or bolts. There are two
categories:
A – Plank boats. An early find is from the British North Ferriby  (c 1700-1500 BC). Oldest Nordic
find is the Hjortspring boat in Denmark (c 300 BC). In Finland, Russia, Karelia and Estonia this
tradition has existed until recent times.
B – Skin boats. One example is the Irish coracle, that was made until the 20th century. Skin
boats were probably only made to a limited extent.
Link. Link.
Sextant
Navigation instrument measuring solar and stellar heights. Used on land
since 16th century – the naval version was developed in 1757 by Captain
John Campbell. The name refers to a sixth of a circumference – 60°. Thus the sextant can measure angles to 120°. The octant operates in a similar way but measures smaller angles.
In wooden shipbuilding, first the hull planks are assembled, then the frames are inserted.
A ship burial or boat grave is a burial in which a ship or boat is used either as a container for the dead and for grave goods, or as
part of the actual grave goods. If the ship is really small, it's called a
boat grave. Examples of ship burials: Abydos,
Khufu, Sutton
Hoo, Vendel, Valsgärde,
Oseberg, and Gokstad
ships.
Ship setting
Burial decorated by a stone setting in the shape of a symbolic ship,
but not containing an actual ship. Swedish examples are Anundshög
and Ales
stenar.
(latin: teredo navalis) This little animal eats wood. It only resides in salt water. Thus
wooden wrecks in the Baltic Sea and sweetwater lakes are spared. More
on degradation.
 Side
scan sonar
This is a sonar that can look sideways. This can be compared with a radar, but uses simple sound
echoes. The beeps are sent from and received to a fish that is pulled after the search ship. The
signals are sent in a wide angular pattern down to the bottom. Thus each pulse lets us
"see" a narrow strip below and to the sides. As the fish advances, an image
is displayed on a monitor or a paper plotter (photo). More info.
Site formation
See decay.
In wooden shipbuilding, first the keel, stem and frames ate raised. Then the hull planks ate
bolted on.
Skin boats
See sewn boats.
 Sonar
Sonar (SOund NAvigation and Ranging) is a simple way to detect wrecks. It uses sound
pulses/echoes, it is inexpensive and can be fitted in small boats. Modern systems can be combined
with GPS. A split-screen function allows for detail studies while keeping the overview. Some sonars
are sediment-penetrating, revealing objects below the seabottom. Image from SMAS
of a wreck.
Stabilisation
The final stage of conservation.
Stern
The rear of a ship where the rudder is located.
The study of layers, sequentially deposited over time. This is very helpful for land
archaeology. Under water it can also be useful, but it's more complicated and often confusing
because of current and sea movement. This is explained in: Archaeology Underwater – the NAS
Guide to Principles and Practice (1992) and Keith Branigan's Archaeology Explained (Duckworth
1973, 1988).
Submerged site archaeology
Maritime archaeology specialising in the study of inundated sites (terrestrial sites which have
been submerged due to land subsidence or rising sea levels). More
info.
Latin: "limit before which". Used in relative dating, when something can be dated
before a certain year. This may be concluded from stratigraphy. If for example wreck A is laying
under wreck B (dated), then wreck A is older than the year of wreck B.
Latin: "limit after which". Used in relative dating, when something can be dated after
a certain year. This may be the case if datable coins are found in an old shipwreck.
Thermoluminiscence
Dating method based on the fact that clay and a few other inorganic materials absorb small
amounts of nuclear energy from natural radiation. The dating involves measuring the amount of
radiation absorbed by a ceramic since it was last fired. This method is mainly used for dating
prehistoric objects. Ref. William R. Biers: Art Artefacts and Chronology in Classical
Archaeology (Routledge 1992)
A well preserved find in its original context can be considered a time
capsule. If carefully investigated it can tell us a story, as if people from times past were
talking to us.
Trawler fishing
Increasing trawler fishing threatens to destroy many shipwrecks.
Treasure hunting
This usually means commercial search for and exploitation of economically valuable items in
historical wrecks. If such treasure is salvaged with no archaeological documentation, in worst case
looted, unique information is ruined for ever. More
info.
Strictly, this means archaeology under water, which is the main discipline of maritime
archaeology. However, the term underwater archaeology is often used in a wider
sense, also covering maritime and nautical archaeology, not necessarily under water. More
info.
Viking age
The last period of the Nordic Iron Age, lasting roughly 800-1050 AD.
 VOC
Verenigde Oostindische Compagnie (Dutch East-India Company), founded in 1602. More
info.
Water dredge
This is similar to an airlift. But it is pumped with water rather than air. It can operate in
more shallow water than the airlift.
Swamps, marshes, bogs and other wetland sites created as a result of changes in the water table
due either to natural or human changes to the environment. More info.
Wetland archaeology
See water saturated sites.
Zebra mussels
Increased activity of this organism seems to threaten shipwrecks in the North American Great
Lakes. Link.
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