What is Geoarchaeology and what can it be used to tell us about where Indus-era people lived?

Hi I’m Joanna, and I am currently studying geoarchaeology for the TwoRains project. I am investigating how water may have flowed around Indus-era sites in northwest India, and how patterns of water flow changed over time.

Water is essential to human life, and where humans choose to live is frequently dictated by water supply. Research suggests that over 50% of the world’s population live within 3 km of a surface fresh water source such as a lake or a river, yet only 3% of continental landmasses are covered by freshwater (Kummu et al., 2011). However, both too little and too much rain can lead to problems for settlements, with drought and flooding affecting their viability.

Monsoon rainfall has a tremendous impact upon life in northwest India, with the increased humidity enabling agriculture in a latitude which could otherwise be expected to be much more arid. However, the amount of rainfall received varies inter-annually as the result of both short-term weather patterns and long-term climate cycles.

Excessive rainfall can cause flooding such as was seen in northwest India in 2010 and 2016. In the past, when water courses were less contained than they are now, flooding could have led to redirection of water flow as river level subsided, and would have led to a highly mobile landscape of changing river pathways.

Flooding in Uttar Pradesh, August 2016: Image Copyright: Indian MoD

On the other hand, decreased periods of rainfall and aridity could lead to far more marginal conditions for agriculture, especially without the modern technology to extract water from deep wells.

So why am I using Geoarchaeology as a tool?

Geoarchaeology is a multi-disciplinary field encompassing methods from both Earth Sciences (Geology, Physical Geography, Hydrology) and Archaeology. Geoarchaeologists can provide insight into the past landscapes that sites are situated in, and how they may have been affected by both past and current environmental processes.

In my research, I am hoping to see which areas of land were perennially wetter and drier and how this may have affected Indus settlements. By using a combination of map analysis, soil samples and sediment sequences, I am assessing which areas of land were wetter, and which were drier, and evaluating how environmental conditions were changing over time.

Both periods of increased and decreased rainfall leave traces in sediment records. Times of increased rainfall see greater river flow and upland erosion, and plants need to be less hardy. In contrast, when there are sustained periods of decreased rainfall, there may be increased wind blown material, there can be desiccation of water sources, and plants which grow need to more drought resistant. Both these changes therefore affect not only the type and size of sediments deposited, but also the geochemistry of sediments.

Studying these changes will allow us to understand how humans have reacted to climate change in the past, and help us to think about how our current reactions to climate change might impact us in the future.