Lowtherville Flashcards
What is the main geological feature occurring at Lowtherville and throughout the undercliff area? Describe it’s mechanism and the impacts on the town of Ventnor because of it.
The primary geological feature is Graben. The primary type of movement occurring is translational sliding along the gault clay to seeward, dipping by roughly 1 to 2 degrees. The shape of the failure surface is a fairly steep rear scarp and an almost horizontal failure plane. The graben feature forms when a mass of material fails in this way and consequently forms a triangular wedge failure behind it in it’s wake which fails through progressively sinking. The wedge is bounded by the faces on either side of it and gradually widens as sinking progresses. This feature can be traced for several hundred metres along the Undercliff area.
Any houses which happen to straddle this graben feature will experience significant distress, begins with cracking and will eventually lead to collapse. Rates of movement can be up to 1cm per year to seeward and is fairly constant. Years of heavy rainfall will lead to increased movement of roughly 50%. Combination of an on-going creep effect coupled with precipitation effects. In the past 20 years the area within Lowtherville has sunk by approximately a metre.
Beneath the road is a major water supply to Ventnor town, any sudden abrupt movements could break the pipe and end up pouring water in to the graben affected area. Not good! The road is also the main link to the hospital. Whole area should be allocated as a high risk land slide area, however has various political issues. Unlikely to get any house insurance cover or mortgage because of it!
