Figure 30. Worm and excrement on mottled 

 clay near Cocos Keeling Island, Indian 

 Ocean. Depth: 5100 m. Photo area: 

 0.6 m x 4 m. Type II camera. 2.4 m target 

 distance. Mounds are 3 cm high. 



Figure 31. Starfish, brittle star, and sea 

 pen on churned silty clay, west slope of 

 Guaymas Basin, Gulf of California. 

 Depth: 911 m. Photo area: 0.6 m y.3 m. 

 Type II camera. 2.4 m target distance. 

 Pits are approximately 15 cm deep and 

 30 cm wide across the openings. 



Burrowing organisms, whether they feed at the sur- 

 face or just below it, digest enormous quantities of sediment. 

 They produce ribbons of excrement (fig. 30) and tunnels 

 that wind around in crisscrossing patterns, evidence of 

 effective extraction of organic matter. The activities of 

 these organisms must have an overall effect on the strength, 

 shear properties, and reflectivity of sediments. Tunnels, 

 voids, changes in porosity, and disruption of grain alignment 

 individually may not be of great importance, but collectively 

 they contribute significantly to the general pattern of the 

 microrelief. 



49 



