Archaeology Magazine - May/June 1990 - 65

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pled surfaces in the deposits. This study suggests that
the center of the second phase of the eruption was south
of the phase one position; we therefore assume the vent
moved south to a new position that was within the sea.
The quantities of lithic fragments from lava flows in
the northern portion of the island, and the thickness
of the phase three deposit, suggest a large volume of
erupted debris, expelled by the collapse that formed the
modern-day caldera north of the Kameni Islands. Phase
four was the final degassing of the magma, carrying
with it whatever solid ash and lithic fragments were
left in the vent.
Like today, Thera had a central bay surrounded by
steep slopes and cliffs of spectacular beauty. During the
Late Bronze Age, however, an extensive land mass existed in what is now the northern sector of the bay. We
are not certain whether this was a broad low plain or a
large island. Before the eruption, the central bay was
open to the sea through the channel that exists today
between Akrotiri peninsula and Aspronisi Island. The
other two channels in today's topography (between Aspronisi and Therasia and between Therasia and Thera)
were created by collapse during the volcanic activity,
most likely in the third phase. The collapse of the chan-

Thera, well below the Late Bronze Age eruptive deposits,
are two distinct white bands of ash and pumice produced
by large explosive eruptions about 100,000 years ago,
both as big as the Late Bronze Age eruption. Collapse
associated with these older eruptions probably formed
the southern caldera. Preservation of the caldera and its
surrounding steep slopes for 100,000 years is not surprising, considering the slow rates of erosion and slope
modification processes in the Mediterranean climate.
Much discussion has been concerned with the effects
of the ash on Crete. By extrapolating from the deep-sea
record, we feel that about two inches of ash were deposited on the central-eastern part of the island, certainly
not enough to cause damage to crops or buildings, and
quickly eroded or mixed into soils.
It would be nice to have some supporting evidence for
our interpretation of the pre-eruptive geography of
Thera, perhaps a snapshot left by the Minoans. We suggest that this may exist in the famous marine fresco of
the ship procession found in the excavation at Akrotiri
(West House, room 5, south wall). Perhaps the town and
countryside depicted on the island at the left edge of
the fresco is the southern part of the bay with either a
stream running off surrounding highlands or a water-

nel between Aspronisi and Therasia islands produced
the major tsunami (seismic sea-wave), which traveled
out toward the southwest passing between Crete and the
Greek mainland. For this we have deep-sea evidence of
redeposited muds stirred by the passage of the tsunami,
and suggests minimal tsunami effects toward the eastern
Mediterranean region.
Thera never had a lofty, centrad, conical peak that collapsed to form the bay we see today. At least two overlapping calderas - an older one to the south, and the
Late Bronze Age caldera to the north (they are topographically distinct below sea level) form today's huge
depression that is flooded by the sea. Small eruptions of
lava from Roman times up until 1950 have formed the
Kameni Islands, which lie along the common boundary
of the two calderas.
Corroborating field evidence for our interpretation
comes from numerous patches of Late Bronze Age volcanic debris mantling slopes that face inward toward the
present-day depression - remnants of pre-Late Bronze
Age eruption caldera walls that formed steep slopes
during Minoan times.
What shaped this earlier caldera, which could have
served the Minoans as a harbor? Exposed in the cliffs of

A fresco from Akrotiri may preserve a asnapshot" of Minoan
Thera beforethe island was devastatedby the Late BronzeAge
eruption of ca. 1628 B.C.
way around the town; in the background are high ridges
and hills much like today (Profitis Ilias) that mark the
older caldera wall; Akrotiri peninsula could be on the
right depicted much as it looks today in terms of topography and color. Clearlyxthere is much conjecture here,
but the Minoans were depicting a landscape that existed
prior to the eruption.
How often do these huge eruptions occur? This is a
major subject of volcanological research and no answer
can be given. On Thera the timing varies between perhaps only a few thousand years to 16,000 years, the span
between the last pre-Late Bronze Age explosive event
that produced a caldera and the Minoan eruption.
When will the next occur? It's hard to say, but when it
does it will be just as dramatic as the eruption witnessed
by the Minoans. We leave for others the problem of what
became of the Therans, forced to flee their island home
and seek refuge on Crete, other Aegean islands, or the
mainland.
May/June1990 49

Archaeology Magazine - May/June 1990

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