A dune is an accumulation of sand in the deserts that are generate by the wind so this is why they have this shapes,they are produced by the wind changes or because of the variation of the amount of sand.When the wind has a dominantdirection, the dunes have a C shape; the advance direction of the dunes is the factor that decides the huge. The small one are the one that go faster, the highest dunes are the one that are 4 or 6 meters. This kind of dunes and these movements you can see in Sechura desert (In Peru).

The movements of the dunes can cause big problems like: the invasion of villages, towns, roads, fields... the best way to control this invasions is to plant trees next and over the dune, other possibility is to spray materials like petrol or some used oils. The first village to do this was the town of villa Gesell in Bonaernse and rhe man who did this kind of experiments was Carlos Idaho Gesell in the Uruguay cost, nowdays cover by pinewoods. But in Spain there some examples too, like Barbate´s pinewood.

What would you do is you where in a village near a dune, and you know that in some moment the dune would invade your house?
This question was the principal one when in 19 century in Barbate the villagers has to plant pines covering a dune.

Earthquakes

The tectonics plates make up the Lithosphere that is the more superficial layer of the earth ,those plates are settled in the astenosphere, that is a liquid layer made up of a hot material; now I'm going to talk about three cities and I'm going to say my opiniof about which is the best one city to live in;

Tokio: Is one of the urban cities more importants of the planet, it has a smaller number of skyscrapers in comparation with other cities of its scale due to the earthquake risk,so the majority of its buildings don't have more than 10 floors;I think even if Tokio is a very well prepared city for a earthquake; I wouldn'r like to live there because it one of the places where more earthquakes happen!

S.Francisco:In 1906 a big earthquake was produced, it devasted S.Francisco , in 1989 another earthquake was produced that killed 250 persons! I neither would like to live there even if the buildings are safer than in toko and they have less probabillities for an earthquake to happen than in tokio

Malaga: In Spain the sismic risk is concentred in the limit between the Euroasiatic plate amd and the African plate , the last earthquake that caused catastrophic damages happened the 25 December in 1884 affecting Malaga and Granada; I would choose Malaga even if its not very well prepared to an earthquake is the place of the ones I've choosen that has less probabillities of an earthquake to happen.