 Now, the waves that we've considered so far are disturbances that occur in a medium. The medium is the substance or material. Water is the medium for an ocean wave. The medium of a stadium wave is people. In a wave, the individual particles or components of the medium are only temporarily displaced. One particle's temporary displacement causes a nearby particle to temporarily displace them, so forth. The particles are not carried by the wave away from their natural position as it returns to their original resting position over and over again. So this wave does not carry particle or medium away, or we say the wave does not transport the particles or the medium from one location to another. The wave only temporarily displaces the medium. One might argue that this is true based upon the following evidence. Despite all the waves in the ocean, there is still water in the middle of the ocean. The wave transports energy. Let's consider only one crest of a wave or a pulse. The pulse is initiated by doing work or putting energy on one side of the medium. This energy is released to their neighboring particles to do work to displace them. This transfer of energy occurs over many particles, over a distance. If the transfer of energy between particles is efficient, the distance that the pulse travels can be very large. If the transfer of energy is not very efficient, say some of the energy is lost in friction, then the pulse does not propagate very far. The pulse transports energy from one side of the medium to the other. You can think of a wave as a consecutive series of pulses, each carrying energy. A wave carries or transports energy. A wave that transfers energy through the displacement of the medium that it passes through is called a mechanical wave. The idealized waves that we've explored are transverse mechanical waves. Transverse because the medium is displaced perpendicular or transverse to the direction of the wave, and mechanical because the wave is a mechanical disturbance of the medium. Now, a striking example of water waves carrying energy is the 2004 Boxing Day tsunami that killed between 240 and 280,000 people living near the coasts of the Indian Ocean. The initial disturbance was an undersea earthquake with a significant vertical displacement of the seabed. This earthquake released an immense amount of energy. The equivalent of roughly 26 megatons of TMT, and this energy was transported by the waves over far distances. Now, in deep ocean water, the tsunami waves form only a small bump, barely noticeable, but those waves travel at very high speeds of between 500 and 1,000 kilometers per hour. Radar satellites recorded heights of these small waves in deep ocean of only about 60 centimeters or two feet, some two hours after the initial earthquake. But in shallow water, near coastlines, that wave slows down to only tens of kilometers per hour, but in doing so it forms large destructive waves. Scientists investigating the damage in Ache found evidence that the wave reached a height of 24 to 30 meters, that's in excess of 100 feet. A lot of the energy released by the earthquake was dissipated or used in traveling across the Indian Ocean, but a whopping 20% of the earthquake's energy, the equivalent of roughly 5 megatons of TMT, was unleashed by the tsunami waves crashing onto the coast surrounding the Indian Ocean. Hence, the undersea earthquake's destructive energy was transported to the coastlines of the Indian Ocean by waves.