Sea floor sampling Flashcards
Bottom Dredges
Scrapes the sediment and collects material in a wire or canvas bag
Grab samplers
Take a ‘bite’ out of the sediment covering the bottom
What volume can the box corer gather?
Up to 60cm of sediment
What volume can the Multicorer gather?
Up to 60cm
Gravity and piston corers
Use a weight to drive a core barrel into a soft bottom
Why do piston corers take longer cores than gravity corers?
Because of the piston in the core barrel
Length of samples taken by gravity and piston cores
About 60m cores
Rotary core drilling
This method is used when core samples of rock are required for detailed analysis. A hollow core barrel is used with a core bit that cuts a cylindrical sample of the rock as the drill bit rotates. This allows for a more complete understanding of the rock strata and its properties.
Rotary open hole drilling
This is a fast and economical method for obtaining soil and rock samples at shallow to medium depths (typically up to 100 meters). It involves continuous rotation of a drill bit to penetrate the ground and utilizes a drilling fluid to flush out cuttings and cool the drill bit.
Gravity corer
= Simple and cheap
-> Weighted metal tube with a coring head is lowered by winch until it falls and penetrates seabed. On impact, collection mechanism triggered.
Length of gravity core
Quite short- <5m
Piston Corer
Used a weighted piston within the coring barrel. As corer penetrates the seabed, piston maintains a constant water pressure inside the barrel to minimise sediment disturbance
Core length- Piston corer
5-20m
Multicorer
Collects multiple short cores simultaneously
–> Frame holding several coring tubes collecting samples <5m
Grab sampler
- Useful for collecting surface sediment
= 2 metal jaws that snap shut on contact w. seabed
