Back to Science & Technology for Exploration

Sediment Cores

A sediment core is a sample of mud, sand, or other loose material collected from the bottom of a body of water. Scientists use sediment cores collected from the ocean to study seafloor geology, chemistry, and biology.

A blue crate filled with vertical push core tubes with colored handles, positioned on the ocean floor, is being approached by a robotic arm in a deep-sea environment.

Remotely operated vehicle Odysseus with collected push cores. Image captured by ROV Odysseus, courtesy of Microbial Stowaways. Download largest version (jpg, 877 KB).

How Do Sediment Cores Work?

There are many different ways to collect seafloor sediment for study. Two of the most common methods used by deep-ocean explorers are “push cores” and “box cores.”

Taking a push core involves pressing a long, transparent tube into the seafloor, then carefully extracting the tube to collect a sample of relatively undisturbed sediment. A valve on the tube keeps the sediment from falling out during collection. In the deep ocean, push cores are often collected using remotely operated vehicles (ROVs). The ROV pilots on the ship above use the ROV’s manipulator arm to insert and extract push core tubes from the seafloor.

Two scientists aboard a research vessel handle a push core containing a sediment sample. One scientist holds the core, while the second observes. Both are in safety gear, with equipment visible in the background.

Jill Bourque and Samantha Schlegel, scientists with the U.S. Geological Survey, handle a push core containing a sediment sample collected from the seafloor using human occupied vehicle Alvin during the 2025 Aleutian Arc expedition. Image courtesy of The Aleutian Arc: Integrated Exploration of Biodiversity at Priority Benthic Habitats (USGS/BOEM/NOAA/ONR). Photographer: Art Howard. Download largest version (jpg, 1 MB).

Box cores are larger than push cores and require more specialized equipment. They are collected using a “box corer,” a heavy, metal sampling tool that must be lowered from a research vessel by a winch. Upon reaching the seafloor, the box corer’s rectangular collection chamber is lowered into the sediment to collect a large (but still relatively undisturbed) sample. Compared to a push core, a box core provides a bigger picture of what the surface of the seafloor is like. Box cores are also better for collecting rockier, larger-grained sediment.

A team of four researchers operates a yellow box corer on a vessel deck, surrounded by a dark ocean during twilight.

Members of the Gulf of Alaska Seamounts 2019 team surround a box corer. Image courtesy of Brittany Jones, University of Alaska Fairbanks. Download largest version (jpg, 705 KB).

What Happens Next?

Once a sediment core is brought to the surface, it has to be processed, preserved, and studied. Sediment cores are often divided into sections to allow experts to run many different tests. Some scientists examine the geology of the seafloor, while others study ocean chemistry or investigate the tiny organisms living below the surface. Depending on the experiments that need to be done, deep-ocean sediment samples may also be refrigerated to keep heat from affecting the sample’s contents.

Why Are Sediment Cores Important?

Studying the seafloor helps scientists understand ocean chemistry, geology, and food webs, all of which have major impacts on people’s lives. Because seafloor sediments form in layers over time (in some cases very slowly), sampling those sediments can also help us learn about Earth’s geologic past.