did a conflagration of comets contribute dust to the earth and cause climate downturns between 532...

Did a Conflagration of Comets Contribute Dust to the Earth

and Cause Climate Downturnsbetween 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 volcanismNon-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 storms522 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 core3 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 Data-Dancing 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 Mytilene- located 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

Next Set of Historical Data-Comet 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 ocean-otherwise 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 diatoms-

extraterrestrial debris-no Ca-high latitude?• 1 event late 535-536 A.D.-tropical diatoms-

climate 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”

• -local event-no big tree ring signal known

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 Rings-Frost

Starting in Early 536

A.D.

Damaged tree rings536-538 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 dustOur 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 deposits-look 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