Happy Earth Observation Day!

Earth Science Week 2023

Today we are observing landslides using LiDAR technology! Landslides are common in north central Arkansas in Newton, Madison, Washington, and Crawford Counties. They can be identified using Light Detection and Ranging (LiDAR) data that is processed to create digital slope models within ESRI ArcGIS mapping software.

On the above digital slope model, the darker areas indicate steep slopes, whereas lighter areas indicate more gradual slopes. Note the translational landslide located in the center of the image outlined in red. Landslide dimensions are 607 feet in length and 236 feet at its widest point with the toe and flanks clearly visible.

Mass movement of material occurs through a wide variety of processes that result in the downward and outward movement of rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing. Mass movement in Arkansas can be attributed to multiple causes, some of which include weak, weathered, and highly jointed, or faulted bedrock, permeability of the rock material, amount of water, and human interaction.

The photo above shows an example of a landslide south of Jasper, Arkansas between Highway 7 and County Road NC6020 near Newton County Road Department & Fairgrounds.

Geopic of the week: Landslides

Here’s a picture of a recent landslide that took out a gravel road south of Greers Ferry Lake in north central Arkansas.  Landslides are one of the natural phenomenon that earth scientists refer to as geohazards.  It’s impossible to predict where and when a landslide will occur, but there are known conditions that make certain landscapes more prone to sliding.

In Arkansas, conditions that can lead to landslides include steep slopes, and poorly cohesive soil or bedrock – such as shale or alluvium.  Land where vegetation has been cleared is also more likely to fail.  Many landslides occur after periods of prolonged heavy rainfall, though that’s a factor that can’t be avoided.  One of the best ways to determine if an area is prone to landslides is to look for evidence of past slides;  If slopes have failed in the past, it’s likely they will fail again.

If you are developing property or are looking at property to purchase, you should consider whether it is in a landslide prone area.   You can always contact a friendly geologist at the Arkansas Geological Survey and ask them their opinion.