Chapter 27, Problem 1DAA

Tree Rings and Droughts El Malpais National Monument, in west central New Mexico, has pockets of vegetation that have been surrounded by lava fields for about 3,000 years, so they have escaped wildfires, grazing animals, agricultural activity, and logging. Henri Grissino-Mayer generated a 2,129-year annual precipitation record using tree ring data from living and dead trees in this park (FIGURE 27.23).

FIGURE 27.23 A 2.129-year annual precipitation record inferred from com pled tree ring data in El Malpais National Monument Now Mexico. Data ware averaged over 10-yeer intervals; graph correlates with other indicators of rainfall collected in all parts of North America. PDSI, Palmer Drought Severity Index: O, normal rainfall increasing numbers mean increasing excess of rainfall decreasing numbers mean increasing severity of drought

* A severe drought contributed to a series of catastrophic dust stem's that turned the rid western United States into a “oust bow” between 1933 and 1939.

1. Around 770 A. D., the Mayan civilization began to suffer a massive population loss, particularly in the southern lowlands of Mesoamerica. The El Malpais tree ring data show a drought during that time. Was it more or less severe than the “dust bowl” drought?