Etats-Unis Ouest

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# Jour 9: Yellowstone (boucle sud) (21 Jul.)

## Premiers wapitis ("elks" en anglais-américain)

Le wapiti est un mammifère herbivore de la famille des cervidés. Il fait partie des plus grands cervidés du monde avec le sambar mais après l'élan (orignal). Il est presque identique au cerf élaphe d'Europe.
En anglais américain, il est appelé elk, mais ce mot désigne l'élan en anglais britannique, qui est appelé moose aux États-Unis et au Canada anglais.

## Fountain Paint Pot Nature Trail

The Fountain Paint Pot is named for the reds, yellows and browns of the mud in this area. The differing colors are derived from oxidation states of the iron in the mud.[3] As with all hot springs, the heat in the caldera forces pressurized water up through the ground, which is expelled here. Also, rising gasses cause the bubbling action. The bubble action in the mud varies with the seasons. In the early summer, the mud is watery from the high water table due to rain and snow melt. By the end of summer, the mud is much thicker as the water table drops. (source: *https://en.wikipedia.org/wiki/Fountain\_Paint\_Pot* )

## Grand Prismatic Spring

The Grand Prismatic Spring in Yellowstone National Park is the largest hot spring in the United States, and the third largest in the world,[3] after Frying Pan Lake in New Zealand and Boiling Lake in Dominica. (source: *https://en.wikipedia.org/wiki/Grand\_Prismatic\_Spring*)

The spring is approximately 110 m in diameter and is 50 m deep. The spring discharges an estimated 2,100 litres of 70 °C water per minute. (source: *https://en.wikipedia.org/wiki/Grand\_Prismatic\_Spring*)

The vivid colors in the spring are the result of microbial mats around the edges of the mineral-rich water. The mats produce colors ranging from green to red; the amount of color in the microbial mats depends on the ratio of chlorophyll to carotenoids and on the temperature gradient in the runoff. In the summer, the mats tend to be orange and red, whereas in the winter the mats are usually dark green.[8] The center of the pool is sterile due to extreme heat.

The deep blue color of the water in the center of the pool results from the intrinsic blue color of water. The effect is strongest in the center of the spring, because of its sterility and depth. (source: *https://en.wikipedia.org/wiki/Grand\_Prismatic\_Spring*)

# Jour 17: Sunset Crater (28 Jul.)

### Sunset Crater

The date of the eruptions that formed the 340-meter-high cone was initially derived from tree-ring dates, suggesting the eruption began between the growing seasons of A.D. 1064–1065. However, more recent geologic and archaeological evidence places the eruption around A.D. 1085. (source: *https://en.wikipedia.org/wiki/Sunset\_Crater*)

### Wupatki National Monument

Les nombreuses maisons éparpillées sur le site ont été construites par les anciennes populations indiennes de la région, en particulier les Sinagua, à partir du XIIe siècle. Elles vivaient essentiellement de maïs et de potirons cultivés sur le terrain aride sans irrigation. L'agriculture des Sinagua bénéficiait des cendres volcaniques déposées par le Sunset Crater Volcano, qui amélioraient les capacités de rétention d'eau du sol. (source: *https://fr.wikipedia.org/wiki/Wupatki\_National\_Monument*)