shelf - n. a flat area of rock, sand, or ice

iceberg - n. a very large piece of ice floating in the ocean

platform - n. a flat surface that is raised higher than the floor or ground

gradual - adj. moving or changing in small amounts

trend - n. a way of behaving, proceeding, etc., that is developing and becoming more common

according - v. as stated, reported, or recorded by

sample - n. a small amount of something that gives you information about the thing it was taken from