AQUATERRA INCOGNITA: LOST LAND BENEATH THE SEA*
JEROME E. DOBSON
ABSTRACT.The author proposes scientiﬁc recognition of an existing, previously unde-
ﬁned and unnamed global feature. Aquaterra is suggested as the new name for the lands
that were alternately exposed and inundated as ice sheets advanced and retreated over
the past 120,000 years. The vertical amplitude of sea level change amounts to 130 meters,
and the aggregate global area of aquaterra equates to the continent of North America.
The time period coincides with the total span during which modern humans are known
to have existed. Keywords: aquaterra,continental shelf,ice ages.
Many times in the past 120,000 years, continental ice sheets advanced (Pel-
tier 1996; Clark and Mix 2002; Carlson and Clark 2012), and the world ocean
dropped as low as 125 meters below its current level (Frenzel 1973; Fleming and
others 1998; Fleming 2000; Siddall and others 2003; Milne and others 2005; Pel-
tier and Fairbanks 2006; CSIRO 2009). Many times, ice sheets retreated and the
ocean rose, once reaching about 5meters above its current level (Lambeck and
Chappell 2001; CSIRO 2009). Thus, there exists a vast earth feature, equivalent
to North America in size (Table 1), which transforms back and forth among
upland, wetland, and seaﬂoor. The ocean gives and takes like a vast millennial
tide—a long-term, irregular cycle—that has persisted for hundreds of thou-
sands of years and continues today (Douglas 1997; Kemp and others 2011; Lev-
itus and others 2012; Moore and others 2013). Spanning much of the
continental shelf and a small rim of the world’s present coastal lowlands, the
feature remains unnamed, though sizable parts of it are named (Beringia,
Doggerland, Sundaland, and Sahul), and the submerged portion is mostly
unexplored at ﬁne scale. Globally, aquaterra favors the tropics and mid-lati-
tudes (Arctic, 17 percent; northern mid-latitudes, 34 percent; tropics, 38 percent;
southern mid-latitudes, 10 percent; Antarctic, 1percent) and thus clearly would
have been the most desirable place for people to live during the ice ages.
Knowledge of its existence is owed to a handful of geologists, oceanographers,
and other physical scientists who meticulously recorded the evidence of sea
level rises and falls and glacial advances and retreats, but the physical and
human implications of their discovery hardly have been touched.
*I am deeply indebted to Dawn Wright who reviewed two drafts of this paper, one many years ago and one
recent, and gave invaluable advice. I fondly recall many enlightening conversations with Jules W. Delambre
who lived with an abiding interest in the land I call aquaterra and died in 2007 without publishing his
intriguing work: “Beyond land bridges: Exploring the effects of changing sea levels on man during the last ice
age,” presented to the Kentucky Academy of Science on November 21,1986. I appreciate the review and com-
ments of Craig E. Colten, Barry Eakins, and unidentiﬁed peer reviewers, as well as the editorial guidance of
Bimal Paul and Peter Lewis. I thank Ed Martinko, Director of the Kansas Biological Survey, for support and
Jerry Whistler for providing cartographic assistance. Most of all, I appreciate and acknowledge my continuing
conversation with Jeffrey R. Dobson, my partner in this quest for two decades and my brother for even
kDR.DOBSON is professor of geography at the University of Kansas, Lawrence, Kansas 66045;
Geographical Review 104 (2): 123–138, April 2014
Copyright ©2014 by the American Geographical Society of New York
Fifteen years ago, I proposed naming this global feature “aquaterra” and
urged its exploration (Dobson 1999; Dobson and Dobson 1999). It is the tradi-
tional role of geographers to identify, name, deﬁne, and formalize earth
features, just as biologists do for new plant and animal species. The practice
dates from the age of exploration and earlier when new features were added
routinely. The ﬁrst modest step after discovery, then and now, is to give each
place a name, as Martin Waldseem€
uller did when he deﬁned South America as
a continent surrounded by ocean and named it America in 1507 (Wald-
uller 1507; Lester 2009). The next stage is detailed exploration, and the
ﬁnal stage is scientiﬁc investigation. At present, aquaterra is so poorly under-
stood that it might well be labeled “aquaterra incognita,”like “terra incognita”
(remote, unknown landmasses) in the early days of terrestrial exploration. Like
them, it is ripe for exploration.
In this essay, I further deﬁne aquaterra, offer a rationale for its recognition,
and suggest an exploration strategy. The name acknowledges its unique charac-
ter due to the fact that for thousands of years at a stretch it is covered by water
(aqua) and for thousands of years it is exposed as land (terra). This name
avoids any presentist terminology that would view it as submerged land, rising
water, or any other characterization of its present position in the cycle.
Detailed deﬁnitions and territorial geographies of aquaterra will facilitate
studies of physical and human processes during the Late Pleistocene ice ages.
Human migration, for example, can be understood better when the entire
“playing ﬁeld” is known. Human evolution, demic expansions, and the
peopling of landmasses can be understood better if all exposed landforms are
documented, opening to investigation such issues as sighting distances from
island to island (Cavalli-Sforza 1993). Studies of the diffusion of material cul-
ture can be greatly improved by better understanding of explicit pathways
TABLE 1—ESTIMATED AREAS OF AQUATERRA AND THE CONTINENTAL SHELF WITHOUT ADJUSTMENT FOR ESUTAT-
IC RISE AND FALL
EARTH FEATURE ELEVATION/BATHYMETRY AREA*PERCENTAGE
Above current sea level 1-5m17 7.0
At current sea level 020.9
Below current sea level -125 to -1m225 92.1
Total -125 to +5m245 100.0
Overlapping aquaterra -125 to 0m228 84.1
Below aquaterra -200 to 0126 m43 15.9
Total -200 to 0mB 271 100.0
North America (for reference) 243
*In 100,000s of square kilometers.
Source: Calculated by author from Eakins and Sharman (2012, Table 1).
124 GEOGRAPHICAL REVIEW
across aquaterra and advancements within it (Gamble 2013). Island ecology can
be understood as a factor in speciation once missing islands are identiﬁed.
The greatest justiﬁcation, however, is the simple fact that so little is known
about the seacoast where a signiﬁcant portion of humankind surely dwelled for
the better part of 120,000 years. The most startling fact about aquaterra is how
long various depths were exposed without interruption (sea levels based on
Gallup and others 1994; Lambeck and Chappell 2001; Commonwealth Scientiﬁc
and Industrial Research Organisation (CSIRO), 2009). Its upper zone, 25
meters deep, was exposed continuously from about 115,000 BP to 10,000 BP
(Figure 1). Surely this coastal zone that persisted for an uninterrupted period of
105,000 years (88 percent of the time that modern humans are known to have
existed) may have played a vital role in human evolution. For 60,000 years
before 12,000 BP, it never rose above -68 meters. For 35,000 years before 15,000
BP, it never rose above -85 meters. Even at 100 meters depth, the land was
exposed continuously for 12,000 years, more than twice the time span of all
recorded history. These are vast time periods during which much evolution,
physical and cultural, could have occurred and vast territories where people
could have thrived always in relative prosperity compared to farther inland.
Nomenclature and regionalization are essential steps to facilitate communi-
cation, awareness, and action:
•Communication—A primary purpose of this paper is to ignite a dialogue
that will generate support throughout the scientiﬁc community for the explora-
tion and scientiﬁc investigation of aquaterra. Yet, it is difﬁcult even to discuss the
place without appropriate terminology. Customary terms such as “land bridge”
may serve well for local features, but fail to convey the regional and global extent
of vast coastal plains now submerged. Associating the global feature with a spe-
ciﬁc name, such as aquaterra, will focus and clarify the dialogue.
FIG.1—Sea level change since the dawn of modern humans. Sea level sources: CSIRO 2009;
and Lambeck and Chappell 2001.
AQUATERRA INCOGNITA 125
•Awareness—Geography, history, anthropology, archaeology, geology,
biology, and myriad other disciplines are inﬂuenced, knowingly or unknow-
ingly, by the existence of aquaterra. Having a proper name, deﬁnition, and
chronology will provide a common frame of reference for all disciplines.
•Action—Exploration and research are essential. Better communication
and awareness of aquaterra’s physical and cultural realities will, I hope,
motivate scientists of many disciplines to explore, investigate, examine, and
Geographers, cartographers, and oceanographers need to deﬁne this feature at
least as rigorously as the continents traditionally have been deﬁned. Aquaterra
is a global landmass—a feature as distinctive as, for example, the continental
shelf, the Mid-Oceanic Ridge, the Russian steppe, the Andean mountains, or
any individual continent. Aquaterra occupies the upper majority of the conti-
nental shelf and the lower fringe of the current coastal plain of every continent
and island (Figure 2). Over thousands of years, it is at times a vast coastal low-
land; a vast shallow sea; and, in transition, a coastal wetland. Its size—22.5mil-
lion square kilometers (Table 1; or more than 21.0million square kilometers in
Fairbridge 1982; Flemming 1985)—is as great as that of some continents, but it
is not properly a continent due to its discontiguous dispersal about the globe.
All landmasses are deﬁned by time as well as space. This principle is obvi-
ous for paleogeographic conﬁgurations—Pangaea, Gondwanaland, Laurentia—
and applies to the current continents as well. Even in previous geologic eras,
sea level rose and fell due to climate change (Jacobs and Sahagian 1993).
Implicitly, the deﬁnition of North America, for instance, refers to the present;
to an unspeciﬁed past when the current conﬁguration of cratons, shields, terr-
anes, and sedimentary beds were assembled by geologic forces; and to an
unspeciﬁed future when the current conﬁguration surely will evolve into some
distinctly different conﬁguration. The seaward extent of the continental shelf is
FIG.2—Global distribution of aquaterra, based on current bathymetry, ETOPO1-Ice Surface
Data, with no adjustments for eustatic seaﬂoor changes. (Cartography by Jerry Whistler, Kansas
Biological Survey, University of Kansas, using the Mollweide Equal Area Projection).
126 GEOGRAPHICAL REVIEW
deﬁned by a bathymetric contour, typically 200 meters deep, but the location
of that boundary is determined by slope and thus in many locations is rela-
tively insensitive to changes in sea level. As Michael Summerﬁeld (1991,34)
explained, a cumulative frequency distribution of global elevation/bathymetry
“produces a hypsometric curve which...suggests that the true break between
the continents and oceans lies not at present mean sea level but some 200
meters or so lower.”
Aquaterra’s deﬁned space is a function of time. I propose bounding it by
the highest and lowest sea levels of the past 120,000 years. This covers the best-
documented cycles of rise and fall and also the entire span of time during
which modern humans, physically identical to humans of today
, are known to
have existed. Excellent data are available for the most recent sea level rise,
based primarily on analysis of Barbados corals which indicate lows of -120
meters at 17,000 years (Fairbanks 1989) and -125 meters at 21,800 years (Peltier
1994). Some models have predicted levels as low as -135 meters at the Last
Glacial Maximum (Yokoyama and others 2000; Lambeck and others 2002; Pel-
tier 2002) or even -140 meters (Lambeck and Chappell 2001; CSIRO 2009), but
I have chosen to use the more conservative consensus of -125 meters (Fleming
et al., 1998; Fleming 2000; Siddall et al., 2003; Milne et al., 2005; Peltier and
Fairbanks 2006). Earlier Pleistocene ice ages produced even larger modulations,
but I have chosen to emphasize the human connection. Stringer and Gamble
(1993) studied human evolution in relation to glacial cycles inferred from heavy
oxygen isotope (
O) concentrations in marine sediment cores. William Calvin
speculated about the effects of glacial advance and retreat on development of
the human brain (Calvin 1990).
Aquaterra’s deﬁned space is a function of scale. Globally at present, the sea-
ward boundary can be ascertained worldwide at one to twelve kilometers reso-
lution based on global bathymetry data developed by Walter Smith and David
Sandwell, the ﬁnest available bathymetric data for the ocean as a whole (Smith
and Sandwell 1997). ETOPO1bathymetry data (Amante and Eakins 2009,
Eakins and Sharman 2012) at one arc-minute resolution are produced by the
National Oceanic and Atmospheric Administration (NOAA) from satellite
altimetry and ship soundings and can be obtained readily from the National
Geophysical Data Center (NGDC) (Smith and Sandwell 1997). Finer resolution
data are available for certain countries (notably the coasts of the United States,
Australia, France, and the United Kingdom) as well as major sea-transportation
Globally, aquaterra’s inland boundary is imprecise. The Shuttle Radar
Topography Mission (SRTM) provides digital elevation data at 90 meters hori-
zontal resolution for all lands between about 60°N latitude and 56°S (Farr
and others 2007), but its vertical resolution (absolute height error as great as 16
meters) renders it inadequate for this purpose. Even the much ﬁner U.S.
National Elevation Dataset (NED) has a root mean square error (RMSE) of
AQUATERRA INCOGNITA 127
2.44 meters or about half the sea’s maximum elevation above current sea level
at 120,000 years ago. The very shallow zone (0to -10 meters) is especially difﬁ-
cult to register due to the challenges of converting among diverse terrestrial
and marine datums—that is, elevation versus bathymetry.
Aquaterra’s deﬁned space is locally uncertain due to the dynamics of coastal
landforms. The precision of the boundary depends on a thorough understand-
ing of erosion/deposition, seismic, tectonic, and eustatic processes over the past
120,000 years. Changes in global sea level (eustasy) shift massive weights of
water. Transgressions during periods of rising sea level increase the load;
regressions during periods of falling sea level reduce the load. The resulting
changes in eustatic pressure can cause signiﬁcant uplifting or subsidence of
landforms (isostacy) depending on the slope and load-bearing strength of
underlying geologic structures. Coastal landforms occasionally undergo sub-
stantial alterations due to earthquakes and other seismic events caused by
changes in eustatic pressure or by deeper tectonic forces. Notable examples
include the Greek city of Helike which disappeared into the Gulf of Corinth in
373 BC (Soter and Katsonopoulou 2011) and Port Royal, Jamaica, which disap-
peared into the Caribbean Sea in 1692 (Hamilton 2005). When ancient ruins
are found, there is a tendency to dismiss them as subsidence, but scientists
conduct rigorous analyses to determine whether or not subsidence has
In some areas, erosion, deposition, subsidence, and tectonic activity have
raised or lowered land, producing counterintuitive results. Submerged areas
near current shorelines, for instance, may actually have been exposed when the
sea level was higher. Conversely, exposed areas near current shorelines may
have been submerged when the sea level was lower. Even more dramatically,
deltas, barrier reefs, wetlands, and lowland vegetation may have encroached
seaward so that sizable areas of aquaterra are now obscured by land rather than
water. The Nile and Mississippi deltas are dramatic examples. High-latitude
coasts are even more complex due to ever-changing ice cover and isostatic sub-
sidence and uplift (glacial “rebound”).
A long-term goal and major challenge of exploration should be to regional-
ize aquaterra with reference to three-dimensional space and time. In any given
era, aquaterra is either fully inundated during periods of maximum transgres-
sion, as it nearly is today; fully exposed as it was during the maximum regres-
sion 21,800 years ago; or partially inundated and partially exposed.
Regionalization thus depends on creating a reliable chart of dates and corre-
sponding mean sea levels over the past 120,000 years. It is essential, however,
to advance far beyond mere outline. Geographers, cartographers, oceanogra-
phers, and others should map and describe aquaterra’s physical geography,
emphasizing the lands exposed at any given time. Where were its rivers, estuar-
ies, and wetlands? Surely, such water features were focuses of biological activity
and human settlement then as in later historic times. Where were its uplands?
128 GEOGRAPHICAL REVIEW
Surely, elevated areas would have served humans and animals alike as refuges
from ﬂooding, and the theoretical maximum local relief within aquaterra is 125
meters. Where were its distinctive landforms? Waterfalls twice as high as Niag-
ara, cliffs as high as the Hudson River Palisades, and arches as high as Rainbow
Bridge, in Utah, conceivably could have existed there and may have been val-
ued in religious or secular ways.
THE UNKNOWN ZONE
The exposed portion of aquaterra is familiar territory, comprising the coastal
lowlands of every continent and island that modern inhabitants can see, sense,
map, and investigate. The currently submerged portion, however, is the least-
known zone on earth. It is, indeed, less familiar than the surfaces of the Moon
and nearest planets. For comparison, we Earthlings have imaged the surface of
Mars and Venus at 122 meters resolution, yet we have comprehensively mapped
aquaterra’s bathymetry only at one to ten kilometers resolution, and we’ve
imaged hardly any of the submerged portion. This submerged portion can be
further subdivided into a shallow plain less than 50 meters deep, which can be
explored readily by divers, and a deeper plain from 50 to 125 meters, which is
profoundly unknown. Even deep-ocean bottoms are better known due to
explorations in support of submarine operations during the Cold War because
“Blue Ocean” warfare focused primarily on depths below 185 meters.
Another reason for the dearth of information is the difﬁculty of measuring
bathymetry in shallow seas. It is actually easier to measure deep oceans than
shallow seas due to the inherent geometry of active sensors such as sonar. A
signal is emitted from a ship’s sounding device, and the echo returns to a recei-
ver. This limits the angle of incidence to 45
, so that the swath equals the depth
times two. Thus, in deep ocean the swath may be a kilometer or more, while
in aquaterra it is never more than 250 meters. Such a narrow swath means that
a comprehensive survey of any given area requires many tracks. Prior to the
advent of the Global Positioning System (GPS), cartographic control was extre-
mely imprecise. Even with GPS-controlled navigation of survey ships, synthesiz-
ing many narrow tracks into continuous map coverage is technically
demanding. It can be done readily in many coastal areas based on multibeam
sonar sensors and differential GPS, but global coverage is infeasible at present.
Satellite altimetry, based on highly sensitive measurements of gravity, has
replaced sonar as the technique of choice for global bathymetry, but the results
are imprecise for the continental shelf (Smith and Sandwell 1997). The satellite’s
sensor collectively measures the gravity of the total column of core, mantle,
crust, water, and atmosphere beneath each point in its path. An algorithm then
estimates the partial gravity attributable to each component and divides mass
by density to estimate height. In deep ocean, the crust is thin and contributes
relatively little to total gravity, thus imposing relatively little uncertainty on the
water component of the column. Beneath the continental shelf, however, the
AQUATERRA INCOGNITA 129
crust is thick and also may contain irregular geologic structures of unknown
density, thus imposing greater uncertainty on the water component. Also, in
extremely shallow areas shoals interfere with the sensor’s measurements.
The past two decades have seen remarkable advances in measuring shallow
ocean bottom at high resolution through technologies such as autonomous
underwater vehicles and airborne lidar bathymetry (ALB) (Klemas 2013). While
satellite sensing by ALB is technically feasible, investigators currently must rely
on custom surveys by aircraft, and no global database has yet been developed.
Direct visual or photographic observation of the lower plains of aquaterra
is hampered by darkness. Shallow areas can be observed in natural light, but at
100 meters depth light attenuation reduces visibility to 1percent of surface
intensity. Floodlights can be employed by deep divers or with cameras on sub-
mersibles and remotely operated vehicles (ROV) to illuminate features close at
hand, but dependence on active light sources limits perspective. The effect is
comparable to walking through a vast chamber with only a ﬂashlight.
Ancient lost lands—Atlantis, Shangri-La, Mu—rediscovered in all their utopian
glory are standard fare of science ﬁction novels, movies, and television. Society
seems to yearn for some lost connection to an unreported past, yet science
offers little in that vein regarding aquaterra’s lost land, which is known with
certainty to have existed. Instead, conscientious amateurs amass enormous tro-
ves of evidence, only to analyze them with poor standards of proof. Surely it is
time for the scientiﬁc community to reclaim this (literal and ﬁgurative) terri-
tory, for critical analyses of its role in shaping the world we know today.
The geographical signiﬁcance of aquaterra can best be understood though
modern analogies. Consider, for instance, how much land would be lost and
how many people would be displaced if the sea level rose another 125 meters
today. The Mississippi Valley would be ﬁlled as far north as Illinois, the Ama-
zon well into Eastern Peru, and the Ganges halfway across India.
Estimates of future sea level rises are, of course, much less than 125 meters
(Baker and McGowen 2012; Bromirski and others 2012; Powell and others 2012;
Abbott 2013; Bamber and Aspinall 2013; Moore et al., 2013; Parker and others
2013; Webb and others 2013). Rowley and colleagues estimate that a 5meter
rise—equivalent to the maximum inundation at 120,000 BP—would inundate
2.0million square kilometers and displace 376 million people (Rowley and oth-
ers 2009). An extra single meter of rise, for a total of 6meters, would increase
those numbers to 2.1million square kilometers and 431 million people.
PHYSICAL FEATURE VERSUS CULTURAL REGION
Thus far, I have deﬁned aquaterra as a global earth feature in the realm of
physical geography. Here, I will explain how it differs from the continental
shelf and brieﬂy address its human geography.
130 GEOGRAPHICAL REVIEW
In territorial extent, aquaterra is similar to, but not synonymous with, the
continental shelf. Quantitatively, aquaterra occupies 84.1percent of the
continental shelf, plus more than 1.7million square kilometers of uplands and
wetlands above current sea level (Table 1). How does the continental shelf that
overlaps (22.8million square kilometers) differ from the part that does not? It
is tempting to say the deeper part (continental shelf below aquaterra) has never
been exposed, but again time is crucial. It has not been exposed for at least
140,000 years (Figure 1), whereas all of aquaterra has been exposed for at least
some of that time and part of it is still exposed today. Thus, aquaterra has
experienced terrestrial inﬂuences such as direct exposure to wind and rain, ero-
sion and sedimentation, vegetative succession, and human occupance. Addi-
tionally, certain processes that are not exclusively terrestrial, such as glaciation
and volcanic eruption, would have affected exposed portions of aquaterra in
very different ways than the submerged land. All of these inﬂuences are impor-
tant, but human occupance stands out as the most distinctive for how humans
impact the environment and for understanding human origins, both physical
and cultural. Conceptually, aquaterra is to geographical space what the Anthro-
pocene is to time (Crutzen and Stoermer 2000; Syvitski 2012). In both cases,
human occupance is the deﬁning characteristic. Aquaterra was exposed directly
to Anthropocene inﬂuences in a terrestrial environment, while the rest of the
continental shelf was exposed mainly to secondary, aquatic inﬂuences.
Compare the most recent curve of sea level rise against the timeline of cul-
tural innovations (Figure 3), and you will ﬁnd that much human progress
occurred while seacoasts were still quite low. It would not change the timeline
of human progress if, for instance, cities were found as low as -50 meters,
since Jericho is known to have existed when sea levels were that low. Similarly,
FIG.3—Timeline of major cultural innovations in relation to sea level rise over the past
18,000 years. Dates of cultural innovations are taken from various sources, either reputable web-
sites or journal articles, many of which differ regarding precise dates. Hence, they are for general
reference and not meant to be deﬁnitive.
AQUATERRA INCOGNITA 131
a village at -90 meters would merely be contemporaneous with the ﬁrst known
villages in the uplands. More exciting, of course, is the possibility that
precursors of major innovations may exist at even lower depths. One
intriguing possibility is pottery. It would not be surprising to ﬁnd shards as
low as -120 meters, since pottery ﬁrst appeared 18,000 years ago. It would be
remarkable, but not unreasonable, if precursors were found as low as -125
meters since the Venus of Dolnı
´Vĕstonice, Czech Republic, the ﬁrst ﬁred clay
object of any kind, dates much earlier at 27,000 years ago (Stringer and
In terrestrial geography, world regions tend to be deﬁned primarily by
human characteristics (cultures, religions, languages, and the like) with bound-
aries often demarcated by physical features (such as oceans and mountains).
Aquaterra’s unique hybridization of terrestrial and marine geography makes it
amenable to either human or physical regionalization. Certain portions of
aquaterra have been named, and their identities are primarily physical. Berin-
gia, for instance, is simply the portion that lies between Siberia and Alaska;
Doggerland is that which lies in the North Sea and Atlantic Ocean off Western
Europe; Sundaland is that which lies off Southeast Asia surrounding numerous
islands and including the Sunda Straight. At present, not enough is known to
say how they differed culturally from one another.
What is the potential for deﬁning cultural regions throughout aquaterra?
Presently, researchers can infer a few likely characteristics based on the contem-
porary human geography of either adjacent coastal lands or suspected emi-
grants who arrived in other regions as their homelands were being submerged.
In both cases, present knowledge is inadequate, but recognition of aquaterra
will encourage new avenues of research that may yield sufﬁcient knowledge
over time. The greatest need, however, is underwater archaeology in every por-
tion of aquaterra’s physical feature. Examples of successful searches include
physical evidence of rapid inundation of the Black Sea and associated cultural
artifacts found by William Ryan and Walter Pitman (2000) and various cul-
tural artifacts, including sunken ships, found by Robert Marx (1990).
A ﬁrst step toward rational consideration of aquaterra could be enhanced com-
mitment to exploration of the shallow-ocean ﬂoor in its own right. In the pub-
lic mind, ocean exploration primarily means the water column per se and the
deep-ocean bottom. While such interest in the deep unknown is understand-
able and research there is vital and productive, there is an equal need to under-
stand the ocean bottom located closest to our own habitat. Not long ago, the
most conspicuous interest in shallow, underwater exploration was focused on
shipwrecks, especially treasure ships. Today, serious attention is paid to human
artifacts in shallow seas. Aquaterra can be a rallying cry to support and clarify
the efforts of dedicated underwater archaeologists such as those cited by Geoff
132 GEOGRAPHICAL REVIEW
Bailey and Nic Flemming and more broadly to encourage all scholars interested
in studying human and biophysical developments from ancient to modern
times (Bailey and Flemming 2008).
One fruitful avenue of research will be to compare ancient maps and litera-
ture with ancient seacoasts. Conscientious amateurs already do so, but there is
a pressing need for serious, scholarly analyses. If early maps depict ancient
(lower) seacoasts with a precision that is not likely due to random chance, then
either the maps were made earlier than previously recognized or the maps are
based on originals passed down from earlier observers in graphic, written, or
oral form. (It would be unfair to let this topic pass without mentioning the
work of Charles H. Hapgood, who pioneered this type of study and is now
cited frequently in popular literature about Atlantis. It is worth noting that the
foreword of his book, Maps of the Ancient Sea Kings (1966), was written by
John K. Wright, one of the most respected geographers of the 20
Similarly, if ancient documents signal an awareness of sea level rise, then they
too may date from that earlier time or may result from corporate memory per-
sisting longer than previously acknowledged.
Statistics will be an important tool when comparing ancient maps to bathy-
metric contours, but a new statistic is needed for measuring probability-of-ﬁt
(Dobson 2000). What is the probability that any observed similarity between
them is purely accidental? What is the probability that they were drawn inde-
pendently? These questions are analogous to the “torn dollar” puzzle, a long-
time staple of spy stories, in which a dollar bill is torn in half and later
rejoined to prove identity or association. The solution will involve moving the
two paths (representing linear map features in the general case or torn edges in
the analogy) to a common origin, rotating them to achieve the best ﬁt, delimit-
ing the sets of all possible conﬁgurations and all possible intersections, con-
structing a probability surface, and calculating probabilities for exact and
Another fruitful avenue will be to map human habitation sites into readily
accessible geographic information system (GIS) databases with systematic, com-
prehensive, and global coverage. It will be useful to map all purported under-
water structures at high precision with attributes and conﬁdence levels. Indeed,
conscientious amateurs often claim to ﬁnd pyramids, buildings, and roads.
Those claims should be subjected to rigorous conﬁrmation or rejection based
on scholarly standards.
Ultimately, it will be essential to create 3-D geovisualizations of the land
that was lost, carefully noting each temporal phase of sea rise and fall.
These geovisualizations should be global in coverage and should meet the
highest standards of cartographers and geographers. The aquaterra quest will
be as challenging and rewarding as Marie Tharp’s quest to map and visual-
ize the ocean bottom (Felt 2012). In all likelihood, features will be found
that alter societal understanding of human evolution and cultural develop-
AQUATERRA INCOGNITA 133
ment as dramatically as Tharp’s discovery of the Mid-Oceanic Rift altered
geologic theory, resulting in widespread acceptance of continental drift and
The quest to explore the oceans warrants a program as aggressive as the
space program that has constituted a signiﬁcant portion of the U.S. federal
budget since the early 1960s. In 2000, President Clinton convened an Ocean
Exploration Panel of leading ocean explorers, scientists, and educators (NOAA
2012). The panel recommended designating a lead agency to champion the
cause of ocean exploration, establishing an Ocean Exploration Advisory Board,
funding ocean exploration at $75,000,000 per year, and convening a national
Ocean Exploration Forum. Subsequently, the White House and Congress desig-
nated the Department of Commerce, speciﬁcally NOAA, to ﬁll that role. Since
then, NOAA’s Ofﬁce of Ocean Exploration and Research (OER) has been a lea-
der and vocal advocate, but public enthusiasm and political support have been
weak. Funding for the ﬁrst decade amounted cumulatively to only
$185,000,000, far below the panel’s recommended level, and present funding is
only $20,000,000 per year. In contrast, the National Aeronautics and Space
Administration’s (NASA) exploration budget for FY 2012 was $333,700,000 for
research and development, not including systems development and commercial
spaceﬂight (NASA 2013). Even from the most pragmatic, human-safety perspec-
tive, taxpayers would do well to recognize that they are more vulnerable to
unpredictable forces (tsunamis, seismic events, heat and water transfers to the
atmosphere) arising from the seaﬂoor than from, say, asteroids hurtling in
from space. Add to that a deep, abiding interest in human origins, and there’s
a clear justiﬁcation for massive funding.
Logically, NOAA and other ocean-exploration advocates need aquaterra (or
some other new and exciting theme) to stir public interest and broaden sup-
port within the scientiﬁc community. The panel’s report (NOAA 2012) clearly
places human artifacts within the program’s scope, and that can be a founda-
tion for exploring the human geography of aquaterra. Perhaps, for instance,
there will be major thrusts toward understanding what role the shallow seaﬂoor
played in human evolution and cultural development, studying land/sea inter-
changes during the ice ages, and ﬁnding submerged settlements. The current
frame of reference consists of “archaeology” and “social sciences.” Perhaps soon
it will include “ice age,” “civilization,” “inundation,” or other related phrases
such as “sea level.” The ﬁrst national Ocean Exploration Forum was held in
2013, and its report and strategic plan for 2020 will be published soon. I hope
the new Ocean Exploration Advisory Board will include a heightened focus on
aquaterra in future forums, reports, strategic plans, and the President’s
National Ocean Policy Implementation Plan.
Of course, massive funding is not likely to materialize anytime soon due to
the state of the economy and to the inordinate educational effort that will be
necessary to bring the populace and politicians onboard. Meanwhile, a low-cost
134 GEOGRAPHICAL REVIEW
alternative could be a volunteered geographic information (VGI) approach in
which one or more aquaterra mapping centers are established to accept VGI
observations rigorously collected by boaters and divers, enter the observed
depths and features with attributes and conﬁdence levels in a global GIS, and
verify through various means, such as cross-checking of multiple observations
or spot checking with purposeful expeditions.
The exploration and scientiﬁc investigation of aquaterra will require
extraordinary collaboration among geographers and oceanographers. Neither
profession alone is adequately equipped to address the dynamic, physical ocean
below sea level and the dynamic physical and human world above and beside
it. Geographers, for instance, are accustomed to mapping and analyzing road
networks and settlements, but not 3-D columns of ocean water. Oceanogra-
phers are accustomed to studying currents and corals, but not sequent occu-
pance by humans. Oceanographers chart, geographers map, and many
cartographic concepts differ between them. Geographers designed geographic
information systems (GIS) to suit their needs and have been using GIS inten-
sely for decades. Geographer and ocean scientist, Dawn Wright, chief scientist
of ESRI, personiﬁes the type of collaboration that will be needed as she leads a
consensus-building forum on how ESRI’s ArcGIS should evolve to meet the
needs of oceanography (Wright 2002).
It is tempting to say unprecedented collaboration is needed between the two
disciplines, but that would ignore their common origin dating back to antiquity.
For thousands of years, the recognized experts on lands and oceans were called
geographers. In Russia even today, oceanography is one of several key disciplines
comprising the Faculty of Geography at Moscow State University, and joint
expeditions of geographers and oceanographers are widely reported. In the Uni-
ted States, oceanography developed as a separate discipline in the mid-19
tury. Matthew Fontaine Maury, today recognized as “the father of
oceanography,” named his seminal book The Physical Geography of the Sea (1855)
and personally served as vice president of the American Geographical Society
(AGS) in 1854 and 1855 and on the AGS Council from 1859 through 1860. Also,
from 1928 to his death in 1939, Charles R. Crane served on the AGS Council,
funding geographic causes and generously endowing Woods Hole Oceano-
graphic Institution. Hence, it is proper to say that geographers and oceanogra-
phers should collaborate again as they did in the past, and both should reach out
to a variety of complementary disciplines such as archaeology and geophysics.
First, however, the community of interested scholars will need to agree that
the feature exists and give it a name. Aquaterra will serve well.
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