1) Combine together the sugar, pumpkin and spices. Add the yogurt and stir well.
2) With the gingersnaps, line the bottom of a 13x9x2-inch pan.
3) Over the gingersnaps, pour half of the pumpkin mixture.
4) Repeat the layers till the ingredients have all been used up.
5) Freeze the preparation.
6) Allow to mixture to set at room temperature for about 5 minutes, cut into squares and serve. Can be served as a snack. Makes a good coffee accompaniment.