Granular convection

[2] It is sometimes called the Brazil nut effect,[3] when the largest of irregularly shaped particles end up on the surface of a granular material containing a mixture of variously sized objects.

Other studies have used time-lapse CT scans, refractive index matched fluids, and positron emission tracing.

[4] On the lower-tech end of the scale, researchers have also used thin, clear plastic boxes, so that the motion of some objects is directly visible.

Pick as closely as you may, the next plowing turns up a fresh eruption of boulders and pebbles, from the size of a hickory nut to that of a tea-kettle.

These flows can carry material ranging in size from clay to boulders, including woody debris such as logs and tree stumps.

In a serving of mixed nuts , the larger Brazil nuts will often end up on the surface
A demonstration of the Brazil nut effect using a glass jar, a cup of rice, and a stack of coins serving as the intruder initially located at the bottom.
A video demonstrating how shaking a bag of muesli causes the larger ingredients to rise to the surface
Raisins and bran flakes, inside a cereal box. Multiple raisins are visible on top of the flakes
This phenomenon results in raisins tending to rise to the top of a box of breakfast cereal , so that the first servings of the cereal contain more raisins than usual, and only flakes are left at the bottom of the box.