Slumping on a Continental Slope Inclined at 1°–4°

Continuous seismic profiles from the upper continental slope east of North Islands, New Zealand, show that surface sediment 10–50 m thick has slumped down bedding planes sloping at 1°–4°. There are four slumps, the Kidnappers Slump which has an area of 250 km2, the Paoanui Slump of 80 km2, a small slump of only several square kilometers and a slump of undetermined extent. All occurred during the last 20,000 years in Last Glacial Age sediments. A glide plane is exposed at the head of each slump and beds are thrust or contorted at the toe of some slumps. Slumping was probably caused by the failure of loosely packed sandy silt during major earthquakes.