224th Street Landslide near Soos Creek Trail EarthCache

A landslide along SE 224th Street near the Soos Creek Trail

The landslide of SE 224th Street provides an opportunity to observe the features of a small landslide up close.

Educational objectives:
Learn 3 different type of landslides.
Learn characteristics of landslides.
Identify the type of landslide here.
Identify the type of mass movement that took place.

HISTORY:
Before 1998, SE 224th Street was a through street at this location. In January 1998 the ground moved about 3 feet and in December 1998 it moved up to 15 feet horizontally. The landslide affected not only the landowners on the hillside, but also the Bonneville Power Administration who had a major power pole in the path of the landslide. They relocated the pole in early 1999.

Please respect the property owners on the sides of SE 224th and stay on the street access.

- PARTS OF A LANDSLIDE:

- TRANSLATIONAL LANDSLIDE:






- ROTATIONAL or SLUMP LANDSLIDE:





- ROCKFALL LANDSLIDE:

Additional parts of a landslide are shown in the diagram to the right. These include:

• Zone of Depletion – The area where the rocks or earth moves out.
• Zone of Accumulation - The area where the rock or earth is deposited.
• Surface of Rupture or the slip plane - The surface that the rocks slide across.
• Head Scarp – The upper edge of the slide above which no movement has occurred.
• Minor Scarp – Places in the slide where differing amounts of vertical movement has occurred resulting in a sharp elevation change.
• Crown Cracks (Tension Cracks) – Separations in the ground surface above the Head Scarp caused by the earth being pulled apart.
• Main Body – The area of the slide with the most movement.
• Transverse Cracks (Tension Cracks) – Separations in the ground surface within the main body of slide caused by the earth being pulled apart.
• Foot – The area of the slide where where the most rock or soil accumulates.
• Toe – The furthest down-slope point there is movement.