The avalanche or nadare is one of the most famous joseki that arises from 3-4 point, high approach, inside contact. The name refers to the typical shape (the similarity will be clearer if you look at the diagram upside-down).
There are several variants, of which the large avalanche can grow quite complex. This joseki has so many variations, and grows to cover such a large area of the board. The other variants typically end up with White getting outside influence. With the exception of small avalanche, the influence will face towards the right side, and White will end up in gote. Therefore, the avalanche is usually played when White has a position at the upper-right corner (e.g., a White stone at the 4-4 point), and is not played when Black has a stone at the top-middle star point.
This much-played variation is known as the large avalanche. It starts a number of complicated variations. See large avalanche for these. If either player wants to avoid these complications, White can play at a or play tenuki (move elsewhere) with , or Black can play at a or b with . These are described in large avalanche simple variations.
With , Black starts the small avalanche. See small avalanche for the continuations.
is advisable for those players who are not comfortable with their knowledge of the avalanche joseki. Black steers the joseki to a simple variation without giving in in any way - the result is equal. See avalanche - connection.
The next variant of the avalanche is when Black plays the double hane of in this diagram. Traditionally, the answer to this move has been a, after which usually Black will try to get influence down the left side, but nowadays the white extension at b is gaining popularity. For the double hane variation, see avalanche - double hane.
is similar to black a in that it is peaceful and takes territory. For this variation, see avalanche - descent.
here would be a mistake. After , White has no good move.