How does Edith Wharton use foreshadowing to prepare the reader for a smashup?Chapter 9 of Ethan Frome

Foreshadowing of the accident begins in Chapter VIII of
Wharton's Ethan Frome as Ethan forms a letter to Zeena explaining
that he is leaving to start a new life out West.  However, Ethan halts his writing as
the realization comes to him that his farm is heavily mortgaged and he will have an
impossible task to pay this and make a living for himself and Mattie both if he goes. 
Then, too, he considers that Zeena would have nothing.  With despair, he
concludes,

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There was no way out--none.  He was a prisoner
for life, and now his one ray of light was to be
extinguished.

Certainly, this
thought with the final word of extinguished is suggestive of
an ending.  When Ethan is determined to take Zeena to the train despite her
protestations, he finds himself distracted as he performs routine
actions. 

Then, descriptions of nature act as
foreshadowing. As they linger at a place in the woods, they stop at "a shy secret spot,
full of the same dumb melancholy that Ethan felt in his heart."  Here, too, his eye
lights upon "a fallen tree trunk half submerged in snow."  As they walk, "the darkness
descended with them, dropping down like a black veil from the heavy hemlock boughs."
[hemlock is a poison] After they come near the end of the
village,

They
had reached the crest of the Corbury road, and between the indistinct white glimmer of
the church and black curtain of the Varnum spruces the slope stretched away below them
without a sled on its
length.

Here the mention of
the church and the "black curtain" suggest a funeral.  And, that there are no other
sleds hints at the fact that there are no witnesses to see Ethan and Mattie's idea of
sledding. Mattie asks if it not too dark, and Ethan laughs with contempt for nature. 
Even though

it
was the most confusing hour of the eving, the hour when the last clearness from the
upper sky is merged with the rising night in a blue that disguises landmarks and
falsifies distances

he
portentously insists that he can go down with his eyes closed. Mattie tells Ethan,
"What's the good of either of us going anywheres without the other one now?"  She says
she would rather be dead, and Ethan replies that he almost would prefer that.  As they
stand talking, "The spruces swathed them in blackness and silence"--like death. 
Mattie's insistence makes her "the embodied instrument of
fate."

Once on the sled, Ethan sees the big elm,
foreshadowed at the beginning of the chapter with the mention of "the fallen tree
trunk"; but at the same time, Ethan's boast that he can go down with his eyes closed
becomes fulfilling as his attempt to "fetch" the
elm fails.

Clearly, Edith Wharton's highly acclaimed use of
imagery and symbolism create a wonderful tale, while they also serve as foreshadowing
for the fateful accident that creates the tragic irony of the novella's
end.