The wind-blown and fire damaged dead wood from an old bristlecone tree trunk. The trees are age-dated by boring small cylinders of wood through the trunks. Then the annual growth rings can be counted with a dissecting microscope. Comparing the thickness of the annual growth gives an idea of the climatic conditions as well. With the age-dating of living trees and the even more ancient dead ones, the brislecone pine wood preserves a climatic record of about 8000 years.