Chapter 25 The Significance of Contourites for Submarine Slope Stability

Abstract

This chapter discusses the significance of contourites for submarine slope stability. It also provides an overview of environments where the stability of the slope is affected by the distribution and properties of contouritic sediments. Slope instabilities in areas of contouritic deposits are identified on continental slopes, on rises, and in ocean gateways, including some of the largest submarine landslides known. Thermohaline and geostrophic circulation affect surface-water masses, so that the continental shelf and the upper continental slope may also be influenced by the action of bottom currents, such as offshore Norway and eastern Canada. The changes in geostrophic and thermohaline currents may also induce the necessary conditions for gas–hydrate dissociation and slope instability. Contourites are deposited on the continental slope during both times of low-stand (glacials) and of high-stand (interglacials) of the sea level. The chapter also discusses the affect of contouritic sediments on the stability of submarine slopes. The submarine slope instability in muddy contourite drifts on northern, high-latitude slopes, of elongated drift mounds on southern high-latitude continental slopes and rises and in sediment drifts in areas of ocean gateways are also addressed.