556 



Internal Waves 



survey. The internal standing wave originates near the entrance of the Gulf 

 as a superposition of two progressive waves of 1000 km wave length and 

 a velocity of progress of 175 cm/sec. The velocity decreases considerably to- 

 wards the interior of the Gulf. It is interesting to note that this standing wave 

 reflects itself clearly in the sediments of the Gulf. The coarser sediments 

 are deposited along the three nodal lines, where the velocities are great 

 (up to 20 cm/sec), while the finer sediments are collected at the anti-nodes 

 of the oscillations. This difference in the size of the grains of the sediments 

 in a horizontal direction suggests that the standing wave within the Gulf 

 might be a phenomenon which occurs frequently (Revelle, 1939, p. 1929). 



400 600 



km 



200 400 600 800 1000 



km 



Fig. 231. 

 ferred to 



Vertical distribution of the density a, and profiles of the isobaric surfaces (re- 

 the 1 500 deci-bar surface) along a longitudinal section of the Gulf of California 



(Sverdrup). 



Munk, in a theoretical investigation, examined the problem of the for- 

 mation of standing oscillations in a bay of variable depth and expanded 

 Fjelstad's theory in this respect. He shows that in this case the expression 

 f(z) • F(x) cos at for the horizontal and vertical velocity (z vertical, x horizontal) 

 have to be replaced by those of the form W(x, z) cos at whereby the problem 

 becomes considerably more complicated. Developing W(x, z) into a Fourier 

 series 



W(x,z) = VC^sin^i 



where 



k = in 1 21 

 and / the length of the bay, the theory requires that all W(z) satisfy analogous 

 differential equations, as in the case of Fjelstad's theory. Furthermore, the 



