Presentation on theme: "Dallas Abbott Lamont-Doherty Earth Observatory of Columbia University"— Presentation transcript:
1Dallas Abbott Lamont-Doherty Earth Observatory of Columbia University Did a Conflagration of Comets Contribute Dust to the Earth and Cause Climate Downturns between 532 and 542 A.D.?Dallas AbbottLamont-Doherty Earth Observatory of Columbia University
2Collaborators Pierre Biscaye-LDEO Jihong ColeDai-Univ. of S. Dakota Dee Breger-Micrographic ArtsRobert Juhl-Tokyo, Japan-Independent ResearcherJohn Barron-US Geological SurveyNashaila Porter-summer intern
3Goals of Talk1) Use historical data on dust storms in China and water chemistry to calendar year date the ice core2) 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.
5Yellow Dust from Asia (including China)-Goes to Greenland
6Insights from Ice Cores Non-seawater sulfate-proxy for volcanismNon-seawater Ca and Mg-proxy for dust from central Asia
7Composition of ice in Greenland -Can we see the Yellow Dust in Mg non seawater? proxy for dust
8Dust 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
9Time Scale of Greenland Ice cores and volcanic source Sulfate anomaly too small-should be bigger-should be at height of red star
10Second 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.
11Ni-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.
12Importance of Ni Earth-most Ni in the core Surface of Earth-typical Ni-parts per millionExtraterrestrial-Ni content at % levelNi visible in spectra-at 1% level or higherLikely source-extraterrestrial material
13Debris from an impact? Native Ni within dust ~536.8±0.2 AD Native elements characteristic of impact
14“large” cosmic debris- quenched cosmic spherule: 534. 7 to 535 A. D “large” cosmic debris- quenched cosmic spherule: to 535 A.D. –enhanced meteor shower?
26536 A.D.-Tropical/Subtropical Microfossils from GISP2 ice core
27Silicoflagellate in 536 AD layer Marine Silicoflagellate Dictyocha stapedia Haeckel (Dave Bukry)Tropical to subtropical species
28Summary1 event-533 A.D.-a few diatoms-extraterrestrial debris-no Ca-high latitude?1 event late A.D.-tropical diatoms-climate downturn-extraterrestrial debris1 event early 537 A.D.-tropical diatoms-still in climate downturn-extraterrestrial debris1 event 538 A.D.-high latitude and Eocene diatoms-extraterrestrial debris-no climate downturn1 event 541 A.D. –tropical diatoms-no extraterrestrial debris-climate downturn
29What 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
30536 A.D. -Climate DownturnMichael 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."
31Tree Rings-Frost Starting in Early 536 A.D. Damaged tree ringsA.D.
32Frost Rings from Bristlecone Pines-500-560 A.D. Ice core
33Source Area for High Latitude Event-Norwegian Sea? 1500 BP tsunami in Shetland islands-right location for Grendel crater candidate
34Insights 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
36Another possibility-round bay in Norway-smaller size
37SummaryIce 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 passesSuggests 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
38ConclusionsThe climate downturn of 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 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.
39Examples 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
40What 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 latitudes2) should be well preserved3) will probably only be a single or a few chevrons-these are small impacts4) send me a jpg and a latitude and longitude