3. You go for a jog on a beach and choose to run near the water, where the sand is well packed and solid under your feet. With each step, you notice that your footprint quickly fills with water, but not water coming in from the ocean. What is this water's source? For what earthquake-related hazard is this phenomenon a good analogy?

Question

Kaya Baldwin

Physics

20 May, 09:57

3. You go for a jog on a beach and choose to run near the water, where the sand is well packed and solid under your feet. With each step, you notice that your footprint quickly fills with water, but not water coming in from the ocean. What is this water's source? For what earthquake-related hazard is this phenomenon a good analogy?

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Answers (2)

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Syllable · Answer 1

The water comes from the displaced sand particles as pressure is exerted on them. The phenomenon is known as Soil Liquefaction

Explanation:

As you jog along the beach close to the seashore, you feet exert pressure on the sand on the seashore. Although the sand on the seashore is well packed together and appear solid under your feet, the pressure exerted on them as you jog causes displacements between the particles of sand, thus forcing water out of the surrounding (remember its a beach, with water just underneath the surface) to fill your footprints

This phenomenon is similar to to the earth-quake related hazard known as Soil Liquefaction.

Soil liquefaction occurs when the soil, which normally is tightly packed and solid, starts behave like a liquid when external force or pressure is applied to it. This displaces the sand particles causing them to lose strength and start to 'flow' like a liquid / The external pressure is usually from an earthquake

Emery Cooke · Answer 2

Liquefaction of soil

Explanation:

A beach is a land form with a body of water which consists of loose particles. Beaches usually occur in areas along the coast where wave or current action deposits and reworks sediments. They could be tide or wave dominated.

The source of the water that fills your footprint is the water that was mixed with the sand you stepped in. On stepping your foot, you forced out sand thereby squeezing it water content into sand away from your footsteps, creating a low potential such that as soon as you raise your foot, the water flows and then fill the void space created.

(B) Liquefaction of soil, occurs where the soil looses strength in response to the stress experienced by your foot step causing subsurface layers to flow and behave like a suspension.