a) Washington Creek aufeis field, 21 June 1977. 



b) Washington Creek aufeis field, 21 June 1977. Note 

 sediment layer on ice inside cavern. 



c) Oregon Creek aufeis field, 7 June 1977. Note sediment 

 layer on melting ice in foreground. 



Figure 53. Potential migration blockages, aufe is fields at 

 Washington Creek and Oregon Creek, June 1977. 



182 



