Question

What are sea and land breezes caused by?

Answer 1

Uneven heating of land and water.

Explanation:

Land and water both absorb energy from the sun. The land heat easier, primarily because it doesn't mix like water does. There are other factors like porousness and reflectiveness at work but we can accept the fact that the land will heat faster than the water.

By mid afternoon the temperature differences are the greatest. This sets up the sea breeze. The heated air over the land will increase in volume (as according to Charles's Law), and since the volume increases the density decreases. The lower density air will be more buoyant than the air over the water which hasn't gotten as warm. This causes the air over the land to rise, and therefore the pressure over the land drops. Air moves from areas of high pressure to low pressure so the air will move from the water to the land.

http://www.weatherworksinc.com/Sea-Breeze

Water not only heats slower than land it cools slower as well. As such by the evening the air over the land will have cold and the volume will then also decrease causing the air to sink. Since the air over the water is still warm it will increase in volume and rise buoyantly. The air then moves from the land to the water.

http://www.proprofs.com/flashcards/story.php?title=113-air-movement_1

I hope this answers your question fully.