Cherry Creek: From Union Station to Alameda

The Millennium Bridge again, but it bears revisiting. The world's first cable stay bridge using post-tensioned construction, I've seen it in engineering texts and lecture videos and at least one movie. It was designed to nestle in amongst the tall buildings of downtown Denver and provide safe passage across a railroad yard. It's the southernmost of three innovative pedestrian bridges to cross the railway, the South Platte River, and an Interstate and connect downtown Denver with the Highlands community.

The span is 130 feet but the deck is only 6 inches thick. It's suspended by cables to a 200 foot mast that acts as a lever anchored to the foundation by cables on the opposite side of the bridge. The deck is 80 feet wide at the average and is supported by I-beams.

The South Platte River bridge and the Highlands pedestrian bridge over Interstate 25 are visible from the Millennium Bridge.

While on the bridge, I checked the weather.

Pressure was dropping but with 30% humidity (from my pocket weather meter, I didn't expect any precipitation or sharp drops in temperature soon.

Here's a closer look at the South Platte River bridge. It's springy enough to feel it as you walk across.

The two major rivers in Denver are the South Platte River and Cherry Creek (I've heard Cherry Creek called "Cherry Creek River" several times and, if South Platte's a River, I guess Cherry Creek might as well be considered a river, too.). This confluence is of historical importance because it's set where Auraria and Denver would be located. The rivers were never large enough to provide economic river traffic (though check out "Venice on the Creek" below!) But it did provide a waterway and convenient sewer for the early settlers.

Cherry Creek is named "Cherry Creek" for the multitudinous choke cherries that grew along it's banks.

There was some hope that this area would yield gold early on, but that dream quickly dissipated. It's there but not in anything like economic quantities.

This guy is about as much responsible for Denver's existence as just about anybody. Little Raven was an Arapahoe chief who welcomed the gold-hunting settlers from (mostly) Georgia to the area and helped them develop a stable community.

You'll notice a lot of things in the Denver area named "Little Raven" and "Arapahoe" (including the Arapahoe County where I live.)

Little Raven tried to establish peace first among the tribes of the Great Plains, with considerable success, and then with the settlers with mixed success. He lived from around 1810 to 1899 so he lived to see conflicts such as the Sand Creek Massacre, and died in a military hospital in Cantonment, Oklahoma. He is buried at Fort Sill, Oklahoma.

I was in familiar territory for the first half mile or so. Here's the row of iron truss foot bridges that connect Speer Avenue with downtown Denver.

These things confused me. There are five and I could see no obvious purpose for them. Best I could figure was that they were a channel for kayakers.

Turns out, that wasn't too far off the mark.

In 1996, the Denver Greenway Foundation launched (heh) an attraction called "Venice on the Creek". They bought five punts (23 foot long wooden boats), hired punters to steer the boats, and installed five dams and locks. It lasted until 2009 when maintenance costs overran the revenue.

Denver's love of murals extend up and down Cherry Creek.

This plaque, embedded in the stone wall lining the creek, explains the origin of the name "Cherry Creek" and some of its history. Although it isn't a mountain stream, it was given to flooding. 

August 3, 1933, a dam near the headwaters of Cherry Creek in Cottonwood Canyon burst and sent a devastating flood into Denver.

The downtown segment of the Cherry Creek trail is usually fairly trafficked by hikers, joggers, bikers and people just trying to get from one place to another. In response, Denver keeps it well maintained and ornamented. 

The trail runs close to many popular downtown sites including the Bellco Theater/Center for the Performing Arts/Denver Convention Center, with their RTD station, and the Auraria Campus.

There's plenty of signage on the trail telling you where you are and how to get to where you're going.

If you're injured on the trail, it runs by the central installation of Denver Health (Denver Health and Hospital Authority) a sprawling, integrated health care facility. It was originally a private hospital but it "bought into" the city government, which caused some problems with procurement so it switched more toward the state and is now a sorta confusing conglomeration of private and public, state and city governed politics. It is governed by an eleven member Board of Directors who are appointed by the Mayor of Denver.

They are a teaching hospital that includes a full range of crisis intervention units. It even has its own Wikipedia page!

https://en.wikipedia.org/wiki/Denver_Health_Medical_Center?wprov=sfla1https://en.wikipedia.org/wiki/Denver_Health_Medical_Center?wprov=sfla1

Ducks abound.....actually waterfowl of many kind including egrets, geese, dippers, and gulls frequent the Denver area. We're on major migration routes and many species have decided that they like the area so much that going further south is just plain silly.

Like many of the streams in the area, Cherry Creek frequently runs through private areas like this Denver Country Club golf course. Then, I have to find my way around. This circumlocution brought me to my final destination, Alameda Avenue.

This little cascade where the creek passes under University Boulevard and into the golf course is man-made but rather picturesque.

A little down the street, the streams runs alongside Cherry Valley shopping center....

And a little further on I rested at a bus stop as I waited for a ride to the Alameda train station. 

The sand bars in the photo indicate that Cherry Creek still carries a considerable load of sediment down to the South Platte River. It travels up to the Missouri that empties into the Mississippi, and then to the Gulf of Mexico and, thus, to the Atlantic Ocean.

This is one of the two big streams in the Denver area and it's fortunate that we have a trail that follows almost it's entire length. There are many natural and historical sites along it.

Streams are fascinating to me. Are there any to explore in your area?

A few photos and notes

While I'm working on some longer posts .....

It's 50° F. and Little Dry Creek is capped with ice. That emphasizes Ice's floating and insulating qualities, some of the properties that makes water so important for life on this planet.

There's a new art installation at Holly Reservoir sponsored by South Suburban Parks and Recreation. "Dichro Rings", by Evan Beloni, is constructed of dichroic materials that reflect light at different colors according to the angle they are viewed. Beloni also calls them "Dichrolions".

I had to pick up a prescription from the King Soopers down the hill on Arapahoe so I turned it into a hike. I often take Little Dry Creek trail to avoid the traffic. It passes by Holly Reservoir. On the way back, I tried out a different approach to Englewood Dam, along South Homestead Parkway.

If you have time, you might walk and turn your errands into hikes 

Rock Identification in the Parks

These rocks aren't from around here.

We don't have many rocks of any size on the ground in my neighborhood that is "from around here." Rockd describes the rock in this area as "colluvium" "generally unconsolidated material deposited on slopes by gravity and sheetwash." It goes down at least 1.5 meters. Little Dry Creek cuts down to a more consolidated bedrock of gravel, sand, silt, and clay called Post-Piney Creek and Piney Creek alluvium. Somewhere down there is the Dawson, Arapahoe, and Denver formations composed of sand and mudstone and shale. It surfaces occasionally to provide the local aquifer.

Nope, no rocks around here.

Except construction material which does provide the budding geologist with samples for practicing rock identification.

There is a lot of this stuff around. The University of Colorado in Boulder is practically made of the stuff and there's a lot in the Tech Center and other places around Denver. Lyons sandstone is pretty, tough, clean, and breaks naturally into nice slabs ready for laying. We have several formations with decent sandstone for building and if you learn about them, it's easy to walk around Denver saying, that building is made from sandstone (or basalt, or marble) from the ________ formation in the _________ area. It can be pretty impressive to visiting friends and family. "Wow! You're smart!"

"Eh. Just flash "

Anyway, the parks, and there are many in the Denver area, are loaded with landscaping stone. Here are some photos and what I think they are. I won't tell where they are. Some could become the target of vandals or collectors.

There's a lot of gneiss (pronounced "nice"). They look sorta igneous because they're full of crystals. Gneisses are formed under great pressure and temperature which causes the crystals to grow and align in those dark and light bands. Some of the oldest rocks in Colorado are gneisses, formed before the land that would be Colorado was even a thing. These were the arcs of volcanic islands that crashed into the North American plate to form Colorado.

The light bands are mostly quartz and feldspar. The dark materials are amphiboles and micas.

I'm thinking this is an aplite vein in gneiss or diabase. Aplite has pretty much the same constituents as granite but tends to be finer grained. Diabase is the coarser grained volcanic rock with a similar makeup as basalt.

This big chunk of sandstone has traveled. To the best of my knowledge, the closest deposit that would be old enough to have sea scorpions in it is south of Colorado Springs. I think the cross shape is worm burrows 

This is a mixed bag, mostly granite and gneiss. I haven't picked through this stuff but I used to find cool specimens in this kind of crushed rock down South.

Here's a pretty, banded mudstone. Mudstones are soft, barely consolidated sedimentary rocks made of, well, mud. A little more pressure and they turn into shale. With added heat and pressure, chemical and physical changes happen to turn the mud into something else, baked clay similar to ceramics, and they become metamorphic slate.

This is the kind of sandstone that forms most of the bedrock in the Denver area. I don't see a lot of it exposed, probably because it isn't particularly pretty. It gets covered over in construction and landscaping projects.

Arcose sandstone is sedimentary rock from eroded granite that still contains many of the minerals unchanged. You can still see grains of quartz and feldspar that hasn't gone to sand and clay. There might even be micas and amphiboles giving it sparkly or darker specks. It forms when weathered products are quickly washed out of the land and buried so that chemical weathering doesn't get a chance to alter it. It's a quickly made sandstone.

The Denver bedrock is an indication of how young the Rockies are (in geological terms) and how quickly they've been carved out.

White rocks are difficult for me. This one has enough crystalization that I want to call it diorite. Diorite is basically a quartz poor granite. I don't see a lot of quartz here but there seems to be mostly chunky feldspar.

It looks like an old boulder. Minerals that contain transition metal ions like iron tend to chemically alter early on and the rusty stains on these rocks are probably from biotite or amphiboles in the original stone.

Much of the "granite" in the Rockies is actually granidiorite, a rock midway between granite and diorite.

So, if you're a budding geologist, don't despise the lowly landscaping stones in your neighbor's garden. Get permission first, and then use them to sharpen your rock identification skills.

Hint: if you run into a problem, you might be able to take a picture and use one of the image identification apps like Google Lens to search for similar images on the Internet.