Mystery of the maya collapse


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  • The oxygen isotopic composition of precipitation and groundwater averages -4 per mil (1/1000).
    Lake Chichancanab averages +4 per mil, indicating that it is 8 per mil enriched in 18O due to evaporation of lake water.
    Lake Punta Laguna averages +1 per mil, indicating about a 5 per mil enrichment.
  • Top: Under conditions of wet climate (low E/P), we expect high lake levels, dilute concentrations of solutes, low 18O to 16Oratios in lake water and aquatic shells, and sediments consisting of mainly organic carbon and calcite.
    Middle: Under conditions of drier climate (moderate E/P), we expect lower lake levels, higher concentrations of dissolved solutes, higher ratios of 18O and 16O, and perhaps sediments dominated by calcite.
    Bottom: Under arid climate conditions (high E/P), we expect low lake levels (perhaps desiccation), high dissolved solute concentrations, high ratios of 18O and 16O and, in the case of Lake Chichancanab, sediments dominated by gypsum (CaSO4).
  • Mystery of the maya collapse

    1. 1. Mystery of the Maya Collapse from Curtis et al. 1997 Scientific Authorship: David Hodell & Lisa M. Lixey As Interpreted by M. Anderson, 2007
    2. 2. Discovery of the Maya Maya cities were deserted, hidden by trees, and virtually unknown until rediscovered in 1839 by a rich American lawyer named John Stevens, who, under appointment by President Martin Van Buren, explored and documented the existence of 44 Mayan sites and cities.  Stevens wrote: “ The city was desolate. No remnant of this race hangs round the ruins….It lay before us like a shattered bark in the midst of the ocean, her mast gone, her name effaced, her crew perished, and none to tell whence she came, to whom she belonged, how long her journey or what caused her destruction….
    3. 3. Discovery of the Maya ….Architecture, sculpture, and painting, all of the arts which embellish, has flourished in this overgrown forest; orators, warriors and statesman, beauty ambition and glory have lived and passed away, and none knew that such things had been or could tell of their past existence….Here was the remains of a cultivated, polished, and peculiar people, who had passed through all the stages incident to the rise and fall of nations; reached their golden age, and perished….
    4. 4. Discovery of the Maya ….We went up to their desolate temples and fallen alters; and wherever we moved we saw the evidence of their taste, their skill in arts….We called back into life the strange people who gazed in sadness from the wall; pictured them, in fanciful costumes and adorned with plumes of feathers, ascending the terraces of the palace and the steps leading to the temples….overgrown with trees for miles around, and without even a name to distinguish it.”
    5. 5. Links between Climate Change and Society Collapse    Copan mound Our society is increasingly interested in the consequences of future climate and environmental changes, as well as the role that humans play in these changes. Human civilizations throughout history have affected the environment (and perhaps influenced climate) through deforestation, agriculture, urbanization and industrialization. In turn, climate events such as droughts, floods, and hurricanes have impacted ancient cultures, both socially and economically.
    6. 6. Maya Civilization   The Maya civilization is one of the best-known ancient civilizations of Mesoamerica. The Maya originated around 2600 BC in the Yucatan peninsula and rose to a cultural and geographical prominence in the classic period (250900 A.D.) when they occupied present-day Chiapas, Guatemala, Belize, Southern Mexico and Western Honduras.
    7. 7.     Maya Culture By borrowing the ideas and tools of neighboring civilizations, the Maya were able to develop sophisticated concepts in the disciplines of astronomy and mathematics. They used this knowledge to construct a calendar system and implemented the mathematical concept of zero. The Maya developed a written language through the use of hieroglyphics and were known for their ceremonial architecture that included temple-pyramids and residential palaces. The Maya were also skilled farmers, potters, and weavers trading and distributing goods with distant peoples. Copan Great Hieroglyphic Stairway
    8. 8.     The Mayan golden age lasted five centuries from 300 to 800 AD. At 800 AD they stopped building temples, declined and became fragmented in competing states. These were easy prey for invading forces from the north such as the Toltec. The Toltecs became the ruling elite of the Maya in the post classic period. Toltec gods were added to the Maya pantheon but the Toltecs were absorbed as they leaned to speak Yucatec Maya. Maya Culture Copan decoration on Temple of Inscriptions
    9. 9.     The Maya were organized in city states, sharing the same beliefs and deferred to priests who derived power from their knowledge of astronomy, mathematics and numerology. The Maya were aware of the passage of time. They recorded some dates on stelae and probably much more in books that are lost now because Spanish Catholic priests destroyed them to eradicate "pagan beliefs". To retrace the history of the Maya we have to rely on whatever clues we can find in what is left of archaeological sites that the Spanish did not plunder or destroy. Maya Culture Copan
    10. 10. Tikal Tikal Temple 1    Deep within the tropical rainforests of Guatemala lies Tikal, one of the largest cities of the Maya civilization. Serving as an administrative, ritual and cultural center for the surrounding urban and agricultural regions, Tikal was home to large populations of people. During the time period between 600 and 800 A.D., Tikal's population grew to as many as 60,000 citizens, making the population density of the city several times greater than the average city in Europe or America during this time.
    11. 11. Tikal Ancient Tikal © Holdell    The city of Tikal occupied a six-square mile area and included as many as 10,000 individual structures, ranging from temple-pyramids to thatched-roof huts. The temple-pyramid was by far the most impressive of the architectural feats and towered above all other structures of the Maya city. Built from hand-cut limestone blocks, the temple-pyramids contained only one or two narrow rooms and mainly was used for ceremonial purposes.
    12. 12. Tikal Tikal Palace © Holdell  The Maya also built low, multi-room buildings, called palaces, that were thought to have served a residential function for the ruling class. This palace is also from Tikal.
    13. 13. Tikal Tikal Temple of the Masks © Holdell
    14. 14. Maya Cultural Periods       The Pre-classic Period: 2000 BC to 250 A.D. The Classic Period: 250 A.D. to 900 A.D. The Post-classic Period: 900 A.D. to the time of Spanish Conquest beginning in 1524 A.D. The Maya culture flourished during the late Classic Period from @ 600 to 800 A.D. The Maya Classic Collapse civilization occurred between 800 and 900 A.D. At this time, all of the large Classic sites in the southern area were abandoned, never to be reoccupied to the same extent as during the Classic Period. Chart: Coe © 1987
    15. 15. Mystery of the Maya Collapse    For over a decade, archaeologists have been trying to unlock the mystery surrounding the collapse of the Ancient Maya civilization. Did human-induced sociopolitical or ecological change cause the collapse of this highly advanced Mesoamerican civilization, or could natural climate variability of the Yucatan Peninsula have contributed to the collapse? Paleoclimatologists are studying the climatic history of this region to provide archaeologists with the climate context in which the Maya civilization evolved, flourished and ultimately collapsed. Tikal
    16. 16. Mystery of Maya Decline Copan Popol Nah Council House     The cause of the Maya decline remains their greatest mystery. Their civilization was not destroyed by an overwhelming outside force. The Maya power disintegrated from within. Many hypotheses have been proposed: overpopulation, famine, epidemics, civil disorder, or could the common people just stopped believing in the dogma the elites were using to establish their power and justify their excesses?
    17. 17. Sociopolitical Causes of Collapse The sociopolitical causes include:  peasant revolts resulting in the overthrowing of the elite class  inter-site warfare between Maya citystates  invasions by peoples from outside the Maya civilization  failure of centralized political authority Copan sacrificial alter
    18. 18. Natural Causes of Collapse Natural causes include factors such as:  soil exhaustion due to slash-and-burn agriculture  water loss and erosion of topsoil evident by increased sedimentation in lakes  natural disasters such as earthquakes and hurricanes  climatic change  disease  insect infestations  overpopulation Copan Great Ball Court
    19. 19. Natural Causes of Collapse Water deficit on the Yucatan © NOAA   When examining the natural causes that could have incited or enhanced the collapse, a further set of both humaninduced and natural climatic factors of the Yucatan Peninsula need to be considered. Some scientists theorize that the paleoclimate of the region was not only different than the present day climate, but that the natural climatic variability of the past could have included a period of intense drought that occurred at the time of the Classic Maya Collapse.
    20. 20. Symptoms of the Collapse Copan East Plaza with Temple of Inscriptions and alter Q; R: Copan East Plaza and Temple 11 with Popol Nah.   Rapid depopulation of the countryside and ceremonial centers in 50 to 100 years, Abandonment of administrative and residential structures,
    21. 21. Symptoms of the Collapse  Cessation of: building construction, carving of sculptured monuments, manufacture of pottery, stonework, jade carvings, Classic calendar and writing systems. Above: Copan temple; Above R: corbeled block-work used by Maya; lBelow R: Copan sculpture.
    22. 22. Yucatan Modern Climate      Before studying the paleoclimate of the region, it is important to understand the region's modern climate. Temperature is uniformly warm on the Yucatan Peninsula with a mean annual temperature of 25o C. Precipitation increases from north to south with minimum values of 500 mm/yr along the NW coast to a maximum of 2500 mm/yr in the southern lowlands. Rainfall is highly seasonal with the rainy season occurring in the summer, May through September, and the dry season during winter, October through April. All of the Yucatan is marked by an annual water deficit that is lowest in the southern Yucatan and highest along the NW coast. Koeppen Climate classification © NOAA
    23. 23. Lake Sediments    The raw material for paleoenvironmental studies is sediment that accumulates in an ordered manner through time and records changes in past climate conditions. The sediments are analogous to a magnetic cassette tape recording, and the challenge for paleoclimatologists is to "play back" the tape. Fossil pollen preserved in lake sediments are often used to reconstruct vegetation changes that can be influenced by climate. Sediment core from Lake Chichancanab
    24. 24. Lake Sediment Cores Scientists reconstructed the past climate of the Maya civilization by studying lake sediment cores on the Yucatan Peninsula. The first area of study, Lake Chichancanab, is located in the center of the Yucatan. Lake Chichancanab is a long (26-km), narrow (2 km) lake, consisting of a series of basins that are connected during high water level. Jason Curtis holding core form Lake Chichancanab
    25. 25. Lake Chichancanab   Sediment cores were collected from the central basin in a water depth of 6.9 m. The lake lies in a fault depression caused by normal faulting. The steep hills on the eastern side of the lake represent the fault line.
    26. 26. Lake Sediments    Pollen cannot be used to reconstruct climate during the Classic Period because the Maya severely altered regional vegetation through clear cutting of the forest for agricultural purposes. It would be impossible to tell, whether a given vegetation change was caused by climate or human agricultural activity. Because of this, scientists rely upon geochemical (elemental and isotopic) evidence for climatic change found trapped in the shells of tiny Crustacea called ostracods.
    27. 27. Oxygen Isotopes       One of the most important tools used to reconstruct the ratio of evaporation to precipitation is oxygen isotopes . Lake water (H2O) contains both the light isotope (16O) and heavy isotope (18O) of the element oxygen. When water evaporates, the lighter isotope (H216O) evaporates at a faster rate than the heavier isotope (H218O) because it has a higher vapor pressure. The reverse happens when water condenses. As long as evaporation equals precipitation over the lake, the lake is at a steady state and the ratio of 18 O to 16O will be constant. However, if climate becomes drier and evaporation exceeds precipitation, the lake volume will be reduced and the ratio of 18O to 16O in lake water will increase. Illustration From Curtis, et al © 2007
    28. 28. Oxygen Isotopes    Alternatively, under wet climatic conditions, the lake level will rise and the ratio of 18O to 16O will decrease. In closed basin lakes, the ratio of 18O to 16O in lake water is controlled mainly by the balance between evaporation and precipitation. The 18O to 16O ratio of lake water is recorded by aquatic organisms, such as gastropods and ostracods that precipitate shells of calcium carbonate (CaCO3). Scientists can measure the 18O to 16O ratio in fossil shells in sediment cores to reconstruct changes in evaporation/precipitation through time, thus inferring climatic change. Illustration © From Curtis, et al © 2007
    29. 29. Hydrology: Closed Basin Lakes    This study consisted of taking sediment cores from two different lakes centrally located on the Yucatan. Both Lakes Chichancanab and Punta Laguna are considered to be closed-basin lakes. The geology of Yucatan is karst (porous limestone), many of the lakes are perched above the water table and isolated hydrologically by clay-basin seals. Illustration From Curtis, et al © 2007
    30. 30.    Closed-basin lakes have simple water budgets, and typically receive water by precipitation, slope wash, and groundwater seepage, while losing a majority of their water through evaporation. Therefore the lake volume, dissolved solute concentrations and oxygen isotopic ratios are largely controlled by the ratio of evaporation to precipitation. This characteristic makes closed-basin lakes climatically sensitive to the changing conditions of evaporation or precipitation. Closed Basin Lakes Illustration From Curtis, et al © 2007
    31. 31. Oxygen Isotope / Rainfall Illustration From Curtis, et al © 2007   This bar chart shows measurements of the oxygen isotopic ratio of modern rainfall and groundwater (blue and magenta) compared to lake water from Chichancanab (white) and Punta Laguna (yellow). The results indicate that a significant amount of water received by Lakes Punta Laguna and Chichancanab was lost to evaporation annually, thereby enriching the lake water in 18O.
    32. 32. Sediment Cores    To retrieve sediment cores from both lakes, two different coring systems were used. For the top most sediments that are water-saturated and oozy, a mud-water interface corer, consisting of a clear polycarbonate tube (125 cm by 7 cm) was used. Deeper sections of the core that occur past the mudwater interface are retrieved in 1 meter intervals using a square-rod piston corer. Similar modified Livingston coring device being used in Trinidad.
    33. 33. Coring Site #2 Holdell    The second lake from which scientists retrieved sediment cores was Lake Punta Laguna, located in the northeastern part of the Yucatan Peninsula about 20 km N-NE of Coba, a major Mayan archaeological site. Punta Laguna consists of three interconnected basins, each with a maximum depth of about 20-m. The coring site was located in the far basin in a water depth of about 6.3-m.
    34. 34. Sedimentation Rates        When the cores are returned to the lab, they are split in two halves. One-half of the core is sampled and the other half is archived for future use. The core that was sampled from Lake Chichancanab had a total length of 4.9 m with a basal radiocarbon age of 9000 years BP. The sedimentation rate averaged about 0.5 mm per year. The core was sampled continuously at 1-cm intervals over its length. A 1-cm sample in the Lake Chichancanab core represents about 20 years of deposition. The sedimentation rate determines the temporal resolution of study and as a result, scientists are able to reconstruct climatic changes that lasted for multiple decades or longer. The sediments of Chichancanab consisted of alternating layers of organic matter, calcite, and gypsum.
    35. 35. Punta Laguna Core     The total core length from Punta Laguna was 6.3m with a basal age of 3300 years. The sedimentation rate averaged 2 mm/year, which is about four times greater than the sedimentation rate in the core from Chichancanab. A 1-cm sample for the Punta Laguna core represents only 5 years of deposition, permitting the resolution of much shorter climatic events. Sediments in the Punta Laguna core are composed almost Above and previous cores are entirely of calcium similar representation taken from carbonate(CaCO3). recent Trinidad expedition.
    36. 36. Dissolved Ions in Lake Water Diagram From Curtis, et al © 2007      This pie diagram illustrates the dissolved ions in lake water from Lake Chichancanab. It is rather salty with total dissolved solids of 4011 mg/L. Chichancanab in Yucatec Mayan means "little sea", which is an appropriate name in light of its saline, sulfate-rich waters. The dominant anion is sulfate (SO4) and the dominant cation is calcium (Ca). Chichancanab is saturated for calcium carbonate and is very close to being saturated for the mineral gypsum (CaSO ).
    37. 37. Punta Laguna Water Chemistry    The water chemistry of Punta Laguna is quite different from Lake Chichancanab. Punta Laguna is relatively fresh with total dissolved solids of 835 mg/L. The dominant anion is bicarbonate (HCO3). The lake water is saturated with respect to calcium carbonate(CaCO3), which many aquatic organisms use to form their shells.
    38. 38. Lake Chichancanab Core Results  Data from the Lake Chichancanab core supports the following interpretation that begins at the base of the core:  From 9200 to 7800 years BP, there was no lake at the coring site as indicated by the absence of aquatic microfossils and the presence of land snails. Beginning at about 7800 years BP, the lake began to fill but the salinity was much higher than today. Evidence for this includes high sulfur content indicating gypsum precipitation, very high 18O and 16O ratios in both ostracods and gastropods, and the occurrence of a benthic foraminifera, Ammonia beccarri. Foraminiferas are almost exclusively marine forms but this species can tolerate a wide range of salinity (7 to 67 ppt); however, it only reproduces between 13 and 40 ppt. The large number of specimens of A. beccarri suggests salinities of at least 13 ppt (the modern lake salinity is only 4 ppt).   
    39. 39. Lake Chichancanab Core Results      The lake basin was filled by 7000 years BP, and relatively wet conditions prevailed from 7000 to 3000 years BP as evidenced by low sulfur, high CaCO3, and low 18O and 16O ratios of ostracods and gastropods. Beginning about 3000 years BP, a drying trend began that culminated in peak arid conditions between 1300 and 1100 years BP. Evidence for climatic drying includes an increase in gypsum (S) precipitation and an increase in 18O and 16O ratios. The peak of this arid event is well dated by an AMS-14C date of a seed taken from the height of the sulfur and oxygen isotope values. The radiocarbon date of the seed is 1140 +/-35 years BP, which translates to a calendar date of 893 A.D. The collapse of the Classic Maya civilization occurred between 800 and 900 A.D.
    40. 40. Data from Lake Chichancanab
    41. 41. From Curtis, et al 2007 © Oxygen Isotope Results    This slide compares the oxygen isotope record on the same species of gastropod between the two lake cores: Punta Laguna (above) and Chichancanab (below). Note that the Punta Laguna record is much higher resolution owing to higher sedimentation rates than Chichancanab. Within the error of the radiocarbon age models, the period of higher mean 18O values in Punta Laguna correlates with the interval of increasing sulfur and oxygen isotope values in Chichancanab.
    42. 42. From Curtis, et al © 2007 Punta Laguna Oxygen Isotope Results The oxygen isotope data measured on ostracods from Punta Laguna sediments have been converted from radiocarbon years to calendar years and compared to Mayan cultural periods.  Superimposed upon the mean changes in the record are distinct peaks that represent arid climate conditions.  These peaks occur at 585 A.D., 862 A.D., 986 A.D., 1051 A.D. and 1391 A.D. Error is approximately +/-50 years.
    43. 43. Ostracod Climate Data From Curtis, et al © 2007
    44. 44. Comparison of Ostracod Data and Maya Cultural Periods From Curtis, et al 2007     The first peak at 585 A.D. coincides with the early/late Classic boundary. This boundary is associated with the "Maya Hiatus", which lasted between 530 and 630 A.D. The Maya Hiatus was marked by a sharp decline in monument carving, abandonment in some areas and social upheaval. This event may have been drought-related.
    45. 45. Comparison of Ostracod Data and Maya Cultural Periods From Curtis, et al 2007    During the next 200 years from 600 to 800 A.D., the late Classic Maya flourished and reached their cultural and artistic apex. The next peak in 18O/16O occurs at 862 A.D. and coincides with the collapse of Classic Maya civilization between 800 and 900 A.D. The earliest Postclassic Period was also relatively dry between 986 and 1051 A.D. At about 1000 A.D., mean oxygen isotope values decrease indicating a return to more humid conditions.
    46. 46. Results   Although a Postclassic resurgence occurred in the northern Yucatan, city-states in the southern lowlands remained sparsely occupied. These findings support a rather strong correlation between times of drought and major cultural discontinuities in Classic Maya civilization. Tikal Temple I and Temple II
    47. 47. © Hodell
    48. 48. Climate and Oxygen Isotope Levels      This illustration shows the simple working assumptions for interpreting changes in the sediment record in terms of climate (evaporation/ precipitation). Top: Under conditions of wet climate (low E/P), we expect high lake levels, dilute concentrations of solutes, low 18O to 16Oratios in lake water and aquatic shells, and sediments consisting of mainly organic carbon and calcite. Middle: Under conditions of drier climate (moderate E/P), we expect lower lake levels, higher concentrations of dissolved solutes, higher ratios of 18O and 16O, and perhaps sediments dominated by calcite. Bottom: Under arid climate conditions (high E/P), we expect low lake levels (perhaps desiccation), high dissolved solute concentrations, high ratios of 18O and 16O and, in the case of Lake Chichancanab, sediments dominated by gypsum (CaSO4).