Most climate scientists agree that over the past century, climate changes that lead to global warming have been caused by human activities. A new study done at Tel Aviv University shows that the earliest known geological signs of human made climate change occurred some 11,500 years ago.
Researchers retrieved a core sample from the Dead Sea and found basin wide erosion rates that are not compatible at all with known climatic and tectonic regimes of the recorded period.
Prof. Shmuel Marco, Head of TAU’s School of Geosciences and team leader noted that the entire planet is now endangered by the impact humans have on the natural environment. This makes it critical to understand the fundamental processes. The team’s discovery make a quantitative assessment available for the start of significant human impact on the Earth’s ecosystems and geology.
Dr. Yin Lu, a post-doctoral student at TAU conducted the research I collaboration with Prof. Nicolas Waldman and Prof. Dani Nadel, both professors of the University of Haifa. The study was done as part of the Dead Sea Deep Drilling project, where a 1,500 foot deep drill core was used to delve into the Dead Sea basin. A sediment record of the last 220,000 years was contained within the core sample.
The erosion that was thus discovered happened during the Neolithic Revolution, when human cultures transitioned of from hunter gatherers to agriculture and settlement on a wide scale. This change caused an exponentially larger human population on the planet.
Prof. Marco explained that crops replaced natural vegetation, animals were domesticated, the natural plant cover was reduced by grazing, and more area for grazing was provided by deforestation. All these factors caused the intensified erosion of the surface resulting in increased sedimentation, which was discovered in the Dead Sea core sample.
The Dead Sea drainage basin acts as a natural laboratory that can be used to understand how sedimentation rates in a deep basin are caused by tectonics, climate change and human made impacts on the landscape.
Prof. Marco also added that the team observed a threefold increase in the fine sand that seasonal floods carried into the Dead Sea. This increased erosion is not compatible with climatic and tectonic regimes during the Holocene, the geological epoch that started after the Pleistocene some 11,700 years ago.
The researchers are now busy extracting the record of earthquakes from the same drill core by identifying disturbances in the sediment layers that resulted from the lake bottom shaking. It will provide the most extensive earthquake record in the world, covering a period of some 220,000 years.