The Colorado River from 30,000 feet altitude

The Colorado River is one of the principal rivers of the southwestern United States. Its headwaters stem from 10,184 ft. (3,104 m) in the Rocky Mountains near Kremmling, Grand County, north-central Colorado. The river traverses five states (Colorado, Utah, Nevada, Arizona, and California, as well as two Mexican states (Baja and Sonora). Its mouth is the Gulf of California (a.k.a. The Sea of Cortez).

There are five dams that interrupt the flow of the Colorado Rivers. Listed from north to south and plotted on the map below are: Glen Canyon Dam, which created Lake Powell; Hoover Dam, which created Lake Mead; Davis Dam, which created Lake Mohave; Parker Dam, which created Lake Havasu; and Imperial Dam, which created Martinez Lake.

When flying over the Colorado River, I am reminded how narrow a river it is. The lakes created by the dams cause modern widening of its size, but in places its narrowness is obvious.

Parker Dam really affects the width of the Colorado River. Upstream from this dam, the river locally widens significantly. Downstream from Parker Dam, the river is much narrower,  especially along the Parker Strip. The next two images are closeups and reinforce these observations.

The field of view in this image is about 35 miles from the top to bottom. The Colorado River in this view is backed up and filled many side canyons upstream from Parker Dam, which is out of the view (farther to the south) in this image.

This image is the farthest to the south among the three images given here. The affect on the width of the river is dramatic below Parker Dam. By the time, the river reaches Mexico, nearly all of the water has been diverted into canals for irrigation purposes. 

Two other dams were proposed between Glen Canyon Dam and Hoover Dam and would have been within the Grand Canyon area, but these dams were abandoned because of environmental damage.

The geologic history of the Colorado River is complicated and remains controversial. Even the timing of its present course is uncertain, but most of its major canyon cutting probably took placed between 5 and 2.5 million years ago.

How to tell the modern crocodilians apart

Crocodiles, alligators [including the closely related caimans], and gharials make up the group of animals known as the modern-day crocodilians.

All crocodilians have at least 60 teeth. Like sharks, they are able to replace lost or worn-out teeth by growing new ones.

Crocodile
Almost all of its teeth "stay" on the outside of its mouth when closed.

Ancient crocodiles lived in southern California during the Eocene, based on fossil remains found in the middle Eocene Santiago Formation in San Diego County. The two teeth shown above are 16 and 17 mm in length (left to right).

Alligator
All of the its lower teeth fit inside the upper ones. When it closes its mouth, only the top teeth can be seen. Its head is broader, flatter, and less triangular than that of a crocodile.

Alligators can live in slightly cooler climates than crocodiles and gharials. Caimans, which belong to the same family as alligators, are native to the Americas, primarily South America.    


Gharial (pronounced GAIR-ee-ul)
It has a very long and very narrow mouth, with over a hundred teeth–more than any other modern-day crocodilian. Unlike the teeth of crocodiles and alligators, a gharial's teeth are all about the same size. Garhials live in India.

Side view of the false gharial Tomistoma schlegelii, 19.75 in. long.
False gharial are freshwater crocodiles found uncommonly today in Malaysia, Boreno, Sumatra, and Java. The snout of T. schlegelii is shorter and more similar to true crocodiles than to the true gharial, but T. schlegelli might be a intermediate form.

Top view of the previous specimen. It is interesting to note that the "holes" in the posterior region of this skull are reminiscent of the supratemporal fenestra ["holes"] found in some dinosaurs (e.g., see my April 23, 2025 post on the skull of the early dinosaur Herrasaurus).