Geology is a crucial component in understanding the context behind the SAR data output that our analysts assess daily. Here's a brief rundown of how geology can help us see the Earth in a new light.
Soils and Rocks Prone to Failure
Clay Soils
Clays are fine-grained and tend to absorb water, swelling as they do so. When saturated, they become much weaker, which makes them prone to landslides and slumping.
Silty Soils
Silt particles are larger than clay but smaller than sand. Silty soils are also prone to becoming waterlogged, and they tend to erode easily when water flows over them.
Loose Sands and Gravel
Sand and gravels, particularly uniformly graded, rounded particles, are prone to failure and erosion in steep slopes. Sand doesn't retain water as clay does, but when saturated with water, is weaker and can liquefy under repetitive load, especially in earthquakes.
Peat and Organic Soil
These are soft and compressible, making them highly prone to subsidence. Organic-rich soils shrink as they dry out, causing ground subsidence, and they lack the strength to support heavy structures without significant ground failure.
Shales
Shale is a fine-grained sedimentary rock that tends to form thin layers. It can become highly fractured and unstable, particularly in wet conditions. Water can infiltrate between the layers, causing the rock to become weak and prone to landslides.
Volcanic Rock
Volcanic rocks that have been formed from fragmented materials, like pyroclastic flows, tend to be loosely consolidated and highly porous.
Rock Formations Prone to Subsidence
Karst Limestone
Karst landscapes, formed primarily in limestone, are particularly prone to subsidence due to the dissolution of the rock by acidic groundwater.
Salt Beds
Salt and other evaporites (like gypsum and anhydrite) can dissolve when exposed to water, leading to significant subsidence.
Rock Formations with Faster Runoff
Pavements and Urbanised Areas
Although not a natural rock formation, human activities that cover the ground with impermeable surfaces (like asphalt or concrete) increase runoff significantly.
Harnessing this Knowledge
Understanding the Terrain
Geology helps us understand what the ground is made of - whether it's rock, clay, sand, or a combination. Different materials respond to forces like gravity or water pressure in different ways. or example, loose soils or clay are more prone to sliding which can trigger landslides, while solid rock may be more stable.
Assessing Slope Stability
Hillsides or mountains are more vulnerable to landslides, especially if the slope is steep and the underlying rock or soil is weak. Geology allows us to analyse the types of rock and soil in those areas to predict whether they are at risk of sliding down during heavy rain or an earthquake.
Evaluating Erosion
Water plays a big role in both landslides and subsidence. If an area has a lot of underground water or experiences a lot of rainfall, it can weaken the ground. Geologists understand how water interacts with different types of soils and rocks, which helps predict areas where water might cause problems, like softening the ground or eroding it.
Combining Satellite Data with Geology
With SAR (Synthetic Aperture Radar) data from satellites, small ground movements can be detected over time. By combining this data with geological knowledge, we can better understand why the ground is moving. For example, if we see displacement near a steep hillside with loose soil, it might indicate that a landslide is developing.
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