Avalanche - double hane
is the a variation of the avalanche joseki. Traditionally, this move was answered with White a, but nowadays White b is considered joseki as well.[1]
After , White captures a stone making shape, while Black takes the key point with
. Next, a is a large point for both, while b is a nice tesuji for Black. Black c is not considered joseki: Black b is better.
Black a is a big move (note that White is not guaranteed to answer it, though), but if Black wants to increase his influence, Black will play at instead. The forceful response of
is White's best answer. Black should not play at
with
, because
makes too good a shape. Neither player should place much importance on the
stones in this variation. White can also play
immediately at
and try to get the best out of the ensuing fight.
If Black plays tenuki, is larger than it looks (a black play at the same point is also large). White threatens to cut at a:
is a peaceful answer. The value of the
stones is even lower than before.
Black can also play atari at before playing
. Although it looks vulgar, this is a viable way of playing. The correct continuation for Black is
: other moves do not work out well. After White captures with a, Black can connect either at b or at c.
is a more recent move in this joseki, but already seems to be at least as popular as White a. Because of the possibility in the next diagram, a working ladder is a prerequisite of this move. In this joseki, White has a large follow-up at b.
is another possibility. The position here is the same as in the small avalanche when White plays at
rather than a. For the follow-up, I refer to that joseki.
[1] I have the impression that recent examples are rare. Charles Matthews