Grades K–2 · Earth & Space
Why are some sandy beaches white and others dark?
Sand is a name for very small grains, not for one single kind of material. Different beaches can have grains made from different rocks, minerals or broken shells.
In the diagramDifferent source materials make different sandpale mineralshell piecesdark rock
Many pale beaches contain lots of light-colored quartz or shell pieces. Some dark beaches contain grains from dark volcanic rock. The grains keep colors related to the material they came from.
Waves and wind can mix and sort these pieces along the shore. A whole beach can look pale, dark or mixed because of its many tiny grains. Its color is a clue about the pieces, not a complete label for each one.
About this explanation
Starting knowledge: Recognize a beach and know that sand is made of many separate grains.
Sources
- National Park Service — Coastal Sediments: Sand Colors