Landscape change in central Mexico Anthony Newton Department of Geography University of Edinburgh

Introduction Long-term research in central Mexico Multidisciplinary research Multiproxy techniques

Collaborators Sarah Metcalfe, Sarah Davis, John Braisby, Nikki Terret, John Farmer, Bob McCulloch (Edinburgh) Phil Barker (Lancaster) Richard Telford (Newcastle) Georgina Endfield, Sarah O’Hara (Nottingham) Melanie Leng (NIGL, Keyworth) Gus MacKenzie, Gordon Cook (SUERC, Glasgow) Charles Frederick (Sheffield) Arturo Chacón and colleagues (UMSNH, Morelia) Ana Lillian Martin del Pozzo and colleagues (UNAM, Mexico City)

Research Themes Volcanology and tephrochronology Volcanic history Impacts on environment and humans Dating and correlation Climate Change Palaeoclimatic record – recent and long-term records Human impacts Pre- and Post-Hispanic

Central Mexico

Areas of research Basin of Mexico Establishment of a tephrochronology Upper Lerma (Toluca) Basin Establishment of a tephrochronology Palaeoenvironmental history Impact of eruptions Michoacán Establishment of a tephrochronology Palaeoenvironmental history Impact of eruptions Impact of Pre- and Post-Hispanic populations on the environment

Trans-Mexican Volcanic Belt

Popocatépetl

Nevado de Toluca

Paricutín

Volcán de Colima

Basin of Mexico To use tephra layers to aid palaeoenvironmental research To establish the hazard posed by surrounding volcanoes 25% of Mexico’s population Popocatépetl (active at the moment) Iztaccihuatl (active during the Holocene) Nevado de Toluca (last active c. 11,000 BP) Numerous cinder cones (Xitle c BP)

Basin of Mexico: Results Tephras from 10 cores Established preliminary tephrochronological framework 2,800 to 34, C years BP Nevado de Toluca and Popocatépetl could pose significant risks Dating and integration with archaeology

Cuicuilco and Xitle Lava

Toluca Basin To use tephra layers to aid palaeoenvironmental research To increase volcanological knowledge of the area Previously no precise analyses of tephra layers Area dominated by the Nevado de Toluca and cinder cone activity

Toluca Basin Tephrastratigraphy

Results 11 late Pleistocene and Holocene tephra layers analysed Tephrochronological framework established New tephra layers found Established link to the Basin of Mexico

Michoacán

Michoacán-Guanajuato Volcanic Field 40,000 km 2 dominated by cinder cones and shield volcanoes 900 monogenetic cinder cones 300 monogenetic shield volcanoes two stratovolcanoes Average of two eruptions per 1000 years cones less than 40,000 years old Paricutín ( ) Jorullo ( )

Tephra impact on lakes Analyse and date the major tephras Assess the response of diatom assemblages to these tephras Develop a response model Consider the impact of tephra on long term environmental reconstruction

Cores and sections of lake sediments and tephra Microprobe analyses of volcanic glass Dating using tephrochronology, 14 C, 210 Pb and historical records High resolution diatom analysis in the context of long-term climate change Methods

Tephras < 1 cm rarely show a response Changes in diatom assemblages short-lived ( years) There is no simple relationship between the Si content of a tephra and a diatom response Available phosphorus varies with tephra inputs Historical tephras show little impact Tephras from cinder cones unlikely to affect long- term lake evolution Conclusions

Exploring ‘The Pristine Myth’ Did the indigenous population alter or degrade their environment? What was the nature of the environmental impact of European settlers? What are the implications for contemporary landscape and resource management?

Pre-Classic: Cuicuilco, Basin of Mexico (< 100 BC)

Classic: Teotihuacán, Basin of Mexico (100 BC – AD)

Teotihuacán

Post-Classic: Tula, Basin of Mexico Toltecs ( AD)

Post-Classic: Cuicuilco, Basin of Mexico Mexica (Aztecs) AD

Post-Classic: Teotenango, Toluca Basin Matlatzinca AD

Teotenango

Post-Classic: Tzintzuntzan, Patzcuaro Tarascans

Modern, Zacapu Chimampas

Colonial 1521 Independence 1821

Tarascan Society

Purépecha ruled by Cazonci Second most important after Aztec Empire Occupied roughly area of the state of Michoacán At time of Spanish conquest the capital at Tzinztuntzan, Patzcuaro 25, ,000 to 100,000 inhabitants Tarascan Society

Population of Patzcuaro area imported food Metallurgical Activity Gold and copper Copper Sculpture and ceramics Relación de Michoacán ( ) Tarascan Society

The Spanish Conquest

First Spanish Soldier - 23 February 1521 Tried to remain autonomous from Spanish Used as a base by Spanish Cazonci executed 14 February 1530 The Spanish Conquest

Methods Palaeoenvironmental records Archives Archaeology Modern environmental studies

Archive Sources Archivo General de la Nacion Tierras land disputes – geographical descriptions, sometimes maps) Inspeccion Occular de Michoacán (1791) »Description of all towns and villages »Ecclesiastical details »Population »Economic activity

Inspeccion Occular de Michoacán Santa Clara del Cobre (near Zirahuén) “… 8 copper foundries each with a work force of between 30 to 40.” Lago de Zirahuén “… with crystal water, healthy and surrounded by peaks covered in pine trees, productive white fish … smaller than those in Laguna de Pazquaro, but superior in quality”

Arocutin “… situated on sterile, high, rough badlands, with miserable huts of stakes or adobe … full of uninhabited ruins.”

20,000 year record: Pátzcuaro

1000 year record: Zirahuén

Zirahuén Conclusions Pre-Hispanic soil erosion Catchment stability during the early Colonial period Accelerated soil erosion, pollution from copper smelting and nutrient enrichment of lake waters have occurred since the mid-18 th century A rapid response to recent land use change.

3000 year record: Zacapu

Continuing Research Interpret archive and palaeoenvironmental results Improve dating of recent sediments and volcanic deposits Work with those studying modern-day processes – decision makers Link on-shore and off-shore sediment sequences Palaeoclimate studies Continue multidisciplinary research