Did a Conflagration of Comets
Contribute Dust to the Earth
and Cause Climate Downturns
between 532 and 542 A.D.?
Dallas Abbott
Lamont-Doherty Earth
Observatory of Columbia
University
Collaborators
•
•
•
•
Pierre Biscaye-LDEO
Jihong ColeDai-Univ. of S. Dakota
Dee Breger-Micrographic Arts
Robert Juhl-Tokyo, Japan-Independent
Researcher
• John Barron-US Geological Survey
• Nashaila Porter-summer intern
Goals of Talk
• 1) Use historical data on dust storms in
China and water chemistry to calendar year
date the ice core
• 2) Use historical data on extraterrestrial
inputs to ice core to test calendar year dates.
• 3) Make a case for multiple comet strikes to
the Earth between 533 and 541 A.D.
• 4) Propose locations for the strikes with most
abundant and unusual diatoms.
Storms of Yellow Dust in
China (500-560 A.D.)
Yellow Dust from Asia (including
China)-Goes to Greenland
Insights from Ice Cores
Non-seawater sulfate-proxy for volcanism
Non-seawater Ca and Mg-proxy for dust from central
Asia
Composition of
ice in Greenland
-Can we see the
Yellow Dust in
Mg non
seawater?
proxy for dust
Dust Storms out of season in
China are rare
Out of season dust storms
522 A.D.-”since the 8th month, yellow dust has
hidden the sun”
535 A.D.-”yellow dust fell like snow”
536 A.D.-”yellow dust fell like snow”
537 A.D.-”rained ashes of a yellow color”
(volcanic?)
None reported until after 547 A.D.
Use dust storms to date GISP2 core
3 year shift-Ca peak is now at 536 A.D.
Small sulfate peak at 537 A.D. when Chinese
reported possible volcanic dust
Time Scale of Greenland Ice
cores and volcanic source
• Sulfate anomaly too small-should be
bigger-should be at height of red star
Second Set of Historical DataDancing with the Stars (Dust)?
• “And the stars in the sky had appeared
dancing in a strange manner and it was
the summer of the year 11 (533 A.D.)
• And it lasted about six or seven years,
until the year three (540 A.D.)”
• Attributed to Zacharias of Mytilenelocated on the Greek island of Lesbos.
• He lived in Greece and Palestine during
his life.
Ni-Fe-Cl-C rich dust from ice core
~533 A.D. (532.9-533.7 A.D.)
Comet observed from Earth on March 1st, 533
A.D., within this time window. Must have been a
close pass-could be comet debris.
Importance of Ni
•
•
•
•
•
Earth-most Ni in the core
Surface of Earth-typical Ni-parts per million
Extraterrestrial-Ni content at % level
Ni visible in spectra-at 1% level or higher
Likely source-extraterrestrial material
Debris from an impact?
• Native Ni within dust ~536.8±0.2 AD
• Native elements characteristic of impact
“large” cosmic debris- quenched
cosmic spherule: 534.7 to 535
A.D. –enhanced meteor shower?
Cosmic Spherule-Dates to
536.6 to 537.0 A.D.
Spherule (right) and native Sn
(bright bottom left)-537 to 537.4
A.D.- comet Feb. 537
Cosmic spherule- from 538.8
to 539.5 A.D. time window
Chronologies Match
with New Time Scale
Ni-rich plus Cosmic Spherules- Comet Dust?
45
5
40
4
35
Fossils, #
30
3
25
# Fossils
20
2
15
10
1
5
0
0
532
534
536
538
Year, A. D.
540
542
NI+cosmic
Next Set of Historical DataComet Observations
Ice core
Comet Sightings and Fossils
in Ice Core
Most fossils in ice core are
diatoms-locations of diatom
rich sediments
Need for shallow water in oceanotherwise impactor too large
Benthic Marine Diatom from
ice core
• Photosynthetic-water depth <100 m
Barite and Zircon Crystals from
Greenland (GISP2 Ice Core)
Continent
Shallow
Water
With Ca data- CaCO3 proxy
536 A.D.-Tropical/Subtropical
Microfossils from GISP2 ice core
Silicoflagellate in 536 AD layer
Marine Silicoflagellate Dictyocha stapedia Haeckel (Dave Bukry)
Tropical to subtropical species
Summary
• 1 event-533 A.D.-a few diatomsextraterrestrial debris-no Ca-high latitude?
• 1 event late 535-536 A.D.-tropical diatomsclimate downturn-extraterrestrial debris
• 1 event early 537 A.D.-tropical diatoms-still
in climate downturn-extraterrestrial debris
• 1 event 538 A.D.-high latitude and Eocene
diatoms-extraterrestrial debris-no climate
downturn
• 1 event 541 A.D. –tropical diatoms-no
extraterrestrial debris-climate downturn
What is Happening-Get
Insights from Historical
Accounts
• 533 A.D. (attributed previously to 536
A.D. but one source says written in 534
A.D.)
• Casiodorus-(Roman)-”The sun seems
to have lost its wonted light and appears
of a bluish color. We marvel to see no
shadows of our bodies at noon, to feel
the mighty vigor of the sun’s heat
wasted into feebleness”
536 A.D. -Climate Downturn
• Michael the Syrian: "the sun was dark
and its darkness lasted for eighteen
months. Each day it shone for about
four hours, and still this light was only a
feeble shadow ... the fruits did not ripen
and the wine tasted like sour grapes."
Tree RingsFrost
Starting in
Early 536
A.D.
Damaged tree
rings
536-538 A.D.
Frost Rings from Bristlecone
Pines-500-560 A.D.
Ice core
Source Area for High Latitude
Event-Norwegian Sea?
1500 BP tsunami in Shetland islands-right
location for Grendel crater candidate
Insights from Legends?
• Monster Grendel-interpreted by Mike
Baillie as a comet• Other legends-3 years without a
summer from Scandinavia• same time as Grendel legend
~6th century
Grendel crater candidate (very
large though)
Another possibility-round bay
in Norway-smaller size
Summary
Ice core samples show evidence of cosmic
influences from 533 to 540 A.D. –Ni rich
comet pieces-this confirms dating from dust
layers.
Cosmic material is found just after comet passes
Suggests close pass of comet to Earth or Earth
orbit (if comet passes plane of Earths orbit
will leave material behind that later can hit
the Earth)
Marine fossil rich layers also found just after
comet passes
Conclusions
The climate downturn of 536-537 A.D. was
probably produced by impact and cosmic dust
Our dating of core puts sulfate rich layer in 537
A.D. (same time as one of Chinese dust
layers).
Origin of climate downturn in 541-542 A.D. is
less clear-something happened to put marine
diatoms into the air but no direct extraterrestrial
debris in ice core (could be an explosive
underwater volcanic eruption).
541 A.D. has a sulfate rich layer-might be from
a volcanic eruption.
Examples of chevrons-point to
source of tsunami
• Chevrons-some are tsunami depositslook redder in close up-those on left
visited last summer– are megatsunami
deposits-contain marine carbonate
What you can do with your
students
• 1) using Google Earth, look for small
chevrons with reddish tint in close up
next to the ocean at low latitudes
• 2) should be well preserved
• 3) will probably only be a single or a few
chevrons-these are small impacts
• 4) send me a jpg and a latitude and
longitude