History of Earth

Tree Rings and Ancient Climatic Conditions

How do archaeologists learn about climatic conditions and their effects on people in the past? In 1815, Mount Tambora in Indonesia erupted so violently that the sound of the eruption could be heard 1,600 miles away. Gases from the volcano shot into the stratosphere almost six miles above the Earth’s surface and lingered for years. Sulfur dioxide combined with water molecules to form sulfate particles that reflected sunlight away from Earth, gradually causing the planet’s surface to cool. The colder temperatures caused severe weather events worldwide.

Understanding Paleoclimate

Climate scientists study evidence in the geologic record, such as fossils, to figure out what climate was like over hundreds of thousands of years (“paleoclimate”). One fossil they use is pollen, a part of a flowering plant that helps make a seed. Pollen can be blown into lakes, where it is preserved in sediment. Pollen from spruces, which do well in cold climates, can suggest what climate was like when spruce pollen was deposited.

Watch Out for Landslides

Landslides not only are dangerous — causing on average more than 25 deaths and over $1 billion in damages a year — but are also widespread, occurring in all 50 states. Compounding the hazards, these natural disasters often occur along with other similar natural phenomena, such as floods or earthquakes. To minimize risk, the slope of land and materials underground must be considered when planning how to build in a community. Altering the slope of land, or even the amount of vegetation on a slope, can have dangerous consequences.

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