A Trip to the Sand Dunes 



Florence Valentine. 

 [See note at beginning of previous article.] 



One crisp Saturday morning our teacher of physiography, 

 took the class on a field trip. We took the train to a small town 

 about half a mile from the sand dunes at the lower end of Lake 

 Michigan. The first question one asks is what the dune is com- 

 posed of and where it gets its material. It is a mound of sand, 

 the material of which is blown up in small quantities from the lake 

 beach by the wind. The sand is weathered rock washed by the 

 lake currents from the bluffs upon the western shore to the south- 

 ern shore of the lake. 



The sand does not remain long upon the beach but is con- 

 stantly moving inland. It is rolled or blown by the wind close to 

 the ground until it meets with some obstacle. A fence or tree 

 trunk often causes the sand to lodge, though a small shrub is the 

 most common. Here the sand lodges and a small mound is 

 formed. The sand is then rolled up the leeward side, which is 

 gradual and falls upon the windward, standing as high as sand 

 will stand. The sand is so fine that even the wind leaves its im- 

 print upon it, in miniature dunes which are sand waves with 

 windward and leeward slopes. This may be seen in Figure 1 

 to a small degree. 



The plant life on a sand dune area is more varied and fas- 

 cinating than one would suppose possible. Upon the shore of the 

 lake there are no vegetables whatsoever, due to the washing of 

 the water and temperature of the ground in that vicinity. A 

 short distance inland there is a sand reed which seems to be 

 native to this region. There are two varieties of this reed, their 

 dift'erence lying in the direction in which their roots grow. The 

 one grows perpendicular, holding the sand from the very base 

 of the small mound, the other spreading its roots wide holding 

 the sand upon the surface compact. One of these reeds is il- 

 lustrated in Figure 2. 



Thus far we have seen only the beginnings of dunes or 

 small mounds. These mounds grow inland in proportion to their 

 height initil thev become dunes. As they recede from the lake 

 region the vegetation becomes more j^lentiful and on the dune 

 flourish dogwood and cottonwood. Although the dogwood is 

 but a shrub, it attains the height of a well grown tree and is not 

 so often buried in the sand as is the cottonwood. This special 

 variety of vegetation has a j^eculiar power which is particularly 

 necessarv to i)l;im lite <in the ever growing sand dtine. As the 



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