GPS check

I had a dentist appointment on the eighth of March, so I took a train and, while I waited at Arapahoe at Village Center station, I compared my GPS coordinates as measured by Google Maps and the Physics Toolbar app. Both are easy. To get the coordinates from Google Maps, you just set a pin on the map where you are...poke your screen at the spot and hold it there until the teardrop shaped pin appears. Then you can read your coordinates in the search bar. Here's what I got.

Physics Toolbox is just as easy. The menu button at the upper left gives you a list of options. Choose GPS and the screen gives you the data. Here's mine.

So what I have from Googles Maps is:

Latitude: 39.600337

Longitude: -104.888418

and from Physics Toolbox:

Latitude: 39.600331

Longitude: -104.888407

That's pretty close, but how does it work out in distance?

There's a formula that gives you the distance between two points, specified by global coordinates on the Earth's surface. In the Astronomy LabBook, it looks like this:

I have it saved in my MC50 Programmable Calculator app so I don't have to crunch the numbers from scratch and my data has the same number of significant digits, so I can punch them right into the calculator. What I get is 0.000024 kilometers. That's 0.024 meters or 2.4 centimeters. Assuming that Google Maps is accurate, Physics Toolbar's stated precision of ± 5.36 meters is pretty conservative. 

Of course, the precision changes according to atmospheric conditions and the number of satellites in range (here we have 20 satellites.) 

GPS is important in any field science. It's easy to note your position in a field notebook when you have a pair of accurate global coordinates, and you should. At each observation you should note your position (if you can't get your coordinates, describe your position as best you can by giving the position in respect to some named landmark) and the date and time.

The smartphone has become a great companion for the field scientist. I never leave home without mine.

Expedition: dry run

Evidently, the term "dry run" originated with fire departments. It denoted a learning exercise in which the team would stage a fire but, since there was actually no fire, they carried no water.

This expedition was a geologist's version of a dry run. I wanted to see how my geology kit felt on my back. I didn't expect to see any outcrops and wasn't disappointed. Mind you, it was a good outing and, although I didn't see any native rocks, I saw plenty of landscaping.

In an attempt to spot any hint of the Dawson formation, I walked up to the intersection of Arapahoe and I-25, where Rockd indicates that the Dawson formation surfaces out of the plentiful colluvium of the area. So I packed my geology kit northeast about a mile to the interchange.

My first stop was Little Dry Creek Park. We've been there before... it's two blocks from my house. Like most parks, this one is landscaped so there are many tastefully placed boulders laying around. These stones are quite obviously not native to the area, but they do offer examples for beginner geologist's to identify.  This one could be granite. There's lots of quartz, feldspar, and biotite, but there's some pretty folding visible on it's side (you might need to zoom in to see it). That pegs it as metamorphic. I'm going to call it gneiss.

A questing pole is like a third leg (or fourth...some folks use two) to help hikers maintain their balance on the trail. For a geologist, it's primary purpose is to give an idea of scale in photographs. 

This box is on the fence where the Little Dry Creek Trail crosses South Xanthus Street. It marks the area as a storm water monitoring site. When I post stream flow data for Little Dry Creek, this is one place it might come from.

Across Yosemite, just a few steps east, the creek branches out in several directions including this swampy spot.

The Dawson formation is the uppermost of three aquifers underlying Denver. Since the area is high desert, it doesn't get a lot of rainfall and the aquifer isn't very productive but it does feed many of the streams.

The rock of the Dawson formation is mostly sandstone with some siltstone. It's the southern extension of the Arapahoe formation that is the primary bedrock under Denver.  Impermeable mudstones and shales under the sandstone hold water in the sandstone, which is why it's an aquifer.

The area around Yosemite has some nice views of the Rockies. The higher you are, the better your perspective, and Yosemite and the parallel interstate highway are at the summit of the eastern rim of the South Platte River valley.

These distant views compliment close-up geology well. For instance, Waterton Canyon is at the far left of this photograph. When you're in the canyon, it's hard to tell whether the rock walls rise to spires or if they are the shoulders of mountains. This view shows the later to be the case. It displays the structure of the Front Range and the relations of its parts.

At the top of the ridge is the Regional Transportation  District light rail and Interstate 25. Just to the north I-25 crosses over Arapahoe Road at an interchange. These types of construction usually require a lot of land shaping, which means that I didn't expect to see much of the Dawson formation or any other native stone in my small expedition.

I do have a soft spot for railroad ballast, the gravel used to cover the beds of train tracks. When I was a kid, I spent a lot of time on railways. Nowadays, they discourage "visitors" because injuries on railways can be expensive. Thus, the fence.

Ballast is usually crushed granite, often large grained granite that has nice crystals of feldspars, epidote, amphiboles, and other minerals. Of course, they don't tell you much about the place where they're found because they're from somewhere else.

This is the kind of "outcroppings" to expect at Interstate exchanges. Colorado, at least, tried to make their highways attractive, in a landscaped, skateboarding park sort of way. But nothing visible is native.

The boulders used for landscaping can be interesting. 

Much of it is granite like this big chunk of white stone.

But, to supplement the earlier photographs of metamorphic and igneous boulders, there was this big piece of mudstone, which may have even been taken from the locality. Notice the banding in the side.

The ripples on the surface indicates that this stone is a top surface of a layer of mud laid down in an aquatic environment.

The Dawson formation is composed mostly of sandstone but includes some mudstone. The layer is about 50 to 100 million years old. During that period, Colorado was under a shallow, inland sea.

On the way back home, I had a few groceries to pick up at the Arapahoe Marketplace Shopping Center. This fellow stands outside.

The sculpture is interesting...a symbol of wild nature made of found materials.

So, this was a dry run to check out the portability of my geology kit. As for the geology, I had no expectations and I didn't get to actually use the kit (except for the trekking pole). But I'm pretty happy with the kit. It only weighs about 4 pounds and fits nicely in my backpack.

The components, from left to right, are a Modular organizer, Husky small parts organizer, Promaster trekking pole, Ozark Trail (Walmart) backpack, and Moto E5 Cruise Android phone.

The Modular organizer carried labels and information pamphlets along with a host of tools. I have a geologist's pick (somewhere) but in the interest of portability, I opted for a multi tool hammer and two chisels (one blade and one conical tipped) for chipping rocks. A set of files are also useful for getting crystals and fossils out of their matrix and for testing hardness (Mohs hardness 6.5). The other multi tool provides, among other things, an accessory knife.

Dental cleaning tools, tweezers, and paint brushes are useful for fine work in cleaning up samples.

I carry my smartphone clip-on microscope to make photomicrographs for the blog and a small beam balance. The spot plate is for quick chemical assays. I can throw small bottles of reagents into the mix as needed. And a ruler and vernier micrometer is there for fine measurements.

I keep my smartphone in a wallet type holder with lots of pockets. Along with a few personal items, There's a note pad, a couple of Fresnel magnifiers, a credit card sized multi tool with cutting edges, a rulers, and some survival information. I also hang a pen, flashlight, and hook/stylus on the lanyard. These are my everyday at-home tools.

Along with the Rockd app, my phone stores the MC50 Programmable Calculator and several measurement tools: AllTrails, Physics Toolbox Pro, the Arduino Science Journal, and the Dioptra theodolite app.

Like astronomy, geology makes a lot of use of angle measurements to describe landforms. Dioptra is the best tool I've found for that.

The Husky organizer is nicely waterproof. I carry my incidental hardware in it...sample containers and padding, Mohs hardness materials, streak plates, magnifiers, microscope slides and cover slips, droppers, a dropper bottle with 10% v/v hydrochloric acid, and anything else I might need on a particular outing.

I also pack some tools in the Husky...a tape measure, IR thermometer, ultraviolet flashlight, and a reflection microscope (the clip-on microscope I carry is a transmission scope.) I also carry a surveyor's compass. It does the same things the Dioptra app does but sometimes the manual operation is more practical than the digital instrument.

It's also a good idea on a geology outing to throw relevant field guides (both general and about your local area) and a topographic and geological map of your area - notice that the Rockd app provides both - into your pack.

So that's my set-up. Yours might be different according to your preferences, finances, or just what you have at hand. For geology on the trail, though, it should be light and I very consciously lean toward inexpensive.

Two of my favorite resources are:

American Science and Surplus

and

Home Science Tools

I also like to cannibalize inexpensive science kits. My IR thermometer came from a Science Wiz kit.

Science Wiz

If you look around, you can probably find most of what you need for geology field work.

Eat your beets...then use the juice to test pH!

As a child, Two things attracted me to chemistry...colorful reactions and fire/explosions. My favorite gifts were science kits and at the top of the list was a chemistry set.

As I got older, I was delighted to find that you didn't need a chemistry set to have fun with chemistry. Everything is composed of chemicals! Check out these colorful reactions.

The big depression in the spot plate is filled with the juice from some beets my son cooked the night before, butter and all! The upper depression has a solution of baking soda. The one below it has tap water. The bottom depression has some rice vinegar in it. The color is from beet juice.

The reason the colors are different is pH. So, what is pH?

p functions (there are many that are used in chemistry) are ways of reporting concentration, especially concentrations of ions in solutions. pH, specifically, tells the concentration of hydrogen ions (that's what the H stands for) in a solution. Acids are substances that place hydrogen ions into a solution; bases are substances that take them out, usually putting hydroxide ions in instead. Concentrated acids and bases are very reactive.

I used to sell car batteries. The sulfuric acid in car batteries will dissolve cotton and turn your skin into parchment. I couldn't keep blue jeans and my knuckles would crack to the bone. A strong base like lye will also take your skin off. Of course, sometimes you want a concentrated acid or base. Strong lye solutions are used in the manufacturing of soap.

The hydrogen ion concentration can range from 0.1 mole per liter in a very concentrated acid to 0.00000000000001 moles per liter in a very basic solution. These numbers are disturbing, but the negative logarithms (base 10) are 1 and 14. That's what a pH is, a negative logarithm, and that's why they're used.

The logarithm (base 10) of 10 is 1, 100 is 2, 1000 is 3, and so on. See? The number of zeros tells you the logarithm. Between each multiple of 10, the logarithms will be between whole numbers. For fractions, the logarithm of 1/10 is -1, 1/100 is -2, 1/1000 is -3, and so on. p function values are negative logarithms so that small numbers will be positive values.

Pure water at room temperature and atmospheric pressure at sea level has a pH of 7 and that is considered neutral because there are the same number of hydrogen ions as there are hydroxide ions. That makes sense because each water molecule splits into a hydrogen ion (actually, each hydrogen ion binds with a water molecule to form a hydronium ion) and a hydrogen ion.

It's nice to have a way to test for acids and bases. Enter beet juice...

Many plants (not just beets) have compounds called anthocyanins. In fact, many of the reds and purples of autumn are from anthocyanins in leaves of trees that are masked during the spring and summer by chlorophyll. Blue and red flowers are often colored by anthocyanins.

But why do they change colors with acids and bases?

Anthocyanins are acids that can lose hydrogen atoms to form basic ions. The neutral molecule and the ion have different colors. In the case of beet juice, it's red when there's a lot of hydrogen ions (in an acid) and yellow when most of the hydrogen is tied up (in a base). Beet juice turns from red to blue to yellow as it becomes less acid and more basic. The yellow color only shows in extremely basic solutions...pH 11 and higher. The sodium bicarbonate solution in the photograph is only weakly basic.

I used to take different colored flowers and hang them above ammonia cleaning fluid, a base, or hydrochloric acid, an acid. The vapors the fluids give off are also basic and acidic. You should try it. The color changes are dramatic.

I would also make violet syrup. If you can find a big patch of violets (don't destroy a whole patch of flowers just to make syrup), pack a Mason jar full and pour hot simple syrup over them (half water and half sugar by volume). Stretch some plastic wrap quickly over the mouth of the jar until it cools (you don't want to lose any of the violet flavor), and then screw the lid on for a day. You'll end up with a dirty blue liquid. That's the basic color. Now add just enough lemon juice to turn the fluid a beautiful magenta. That's the acidic color.  You have a tasty, violet flavored syrup. I think it tastes like wildflower honey.

Moving rocks

On my last hike east, down the hill into Cherry Creek Valley to pick up supplies, I saw a clear demonstration of how ice moves rocks.

Snow had accumulated on the side of the street, freezing under the pile and lifting the material above, including the soil and rocks that had been surrounded.

As it melted, parts of the packed ice sheered away and fell to the side.

The chunks that fell...and scattered...carried those trapped rocks and other debris several inches from where they had been.

Several inches. Big deal. But in geology, we talk blithely about millions and billions of years. This tiny motion has happened billions of times moving land miles away. 

Water and wind work much the same way, getting under stuff and moving it just a little at a time until the land is how you see it.

What are the geological movers and shakers in your area? Look around. Do you see evidence that things have moved around, seemingly on their own? What could have done it? Remember that gravity almost always helps.

How deep is my valley?

Sounds like one of those period dramas, doesn't it?

Of course, I'm still just going on about the Little Dry Creek valley a couple of blocks over from my house.

I've mentioned that the mountain streams in the Rockies are very different than the ones I knew as a child back east. Little Dry Creek, on the other hand, looks very familiar, but all streams have their own personalities. 

On the last walk down the hill, I took some side trips from the main road that parallels the creek, Arapahoe Road, down to the creek to get an idea of the cross sections. You remember that I took one elevation profile down Uinta Street a couple of blogs ago. I supplemented that with three others starting near the rim of the South Platte River valley and stopping at the western end of Walnut Hills, Quebec Street.

Little Dry Creek Park is near the head of the valley where the creek emerges from a culvert under Yosemite Street. On the other side is just storm drainage channels.

Here the creek cuts a shallow channel surrounded by a wide plain. In about 250 feet, there's only a rise of about 10 feet to the surrounding residences. I figure that the plain was carved by the creek because the rise up to the residences have been reinforced by stone to prevent further erosion in that direction.

The headwaters of Little Dry Creek is just building up energy and volume here. There's enough flow to have cut a shallow notch but it looks like it has meandered in the recent past. I doubt if there has been a lot of flooding. The flow has been erratic as shown by water level readings over the last year.

I was in the area in 2020 and 2021 and the maximum flow of 5 cubic feet per second was not enough to flood the creek's banks.

Much of the variance is due to snow melt and occasional spring rains. This data is from the area west of Walnut Hills where the creek passes under Arapahoe Road.

As the creek builds up energy and volume, it cuts a deeper valley with less meandering.

At Uinta Street, the valley drops into the hilly section behind Walnut Hills Elementary School. 

The elevation difference between the top of the hill to the bottom, at Spruce Street, is about 70 feet. The ridge passes through Walnut Hills. It's very visible on Arapahoe.

I would think that it's older than the creek...maybe a bump in the Dawson formation that appears as outcrops northeast and south of Walnut Hills. Regardless, the creek has cut deeply through the ridge. The whole length of the creek has erosion prevention features like small weir dams and boulders that have been moved into the stream bed so the back cutting has been slowed considerably.

I like trying to visualize what different places might have looked like before buildings were there. I wonder if there was a Cascade here.

At the bottom of this grade, Spruce Street crosses the creek.

The creek begins to meander again and there's a wider plain. They're also deeper banks. 

In 0.2 mile, the walk down from Arapahoe only descends about 40 feet. 

The creek begins cutting some fairly deep banks, some about six feet, close to my last stop, Quebec Street at the western boundary of Walnut Hills. These show some nice soil profiles, so I should be coming back later.

Here the valley is broad and the gradient into it is gradual. Over 0.2 miles, the descent is only about 30 feet. On the other side of Quebec, the valley begins deepening again, as shown in the photograph above shot through a fence. (The Little Dry Creek Trail pulls away from the creek for a ways to follow sidewalks around a residential area.)

I have only been looking at the creek valley in Walnut Hills neighborhood. The valley actually extends further on the other side of Arapahoe Road. The rim peaks about a half mile from the creek at Fiddler's Green. Little Dry Creek has slowed down considerably due to erosion controls installed with the residences of Walnut Hill, but it has evidently been much more active in the past 

Now, a few words about the AllTrails app. It's a great tool for measuring distances and elevations but it's not terribly intuitive, so let me give you a few tips. My version is 14.3.1 of AllTrails Pro and I use it on an Android phone version 8.0.0.

Use the Navigate command (the middle button on the toolbar at the bottom of the AllTrails window) to get to the tools. Choose "Start without a route" and choose an activity. Hiking or walking is good. Then just press the start button. When you reach your destination, press and hold Pause and the app will ask you if you are finished. Press Finish. It will ask you how your trip was. On my Android, the app has frozen at this point but, if you close the app and restart it, you will find your data saved in History. Later versions may fix this glitch and it may not happen on other operating systems.

Nevertheless, AllTrails is an excellent app to measure the shape of your landscape. There is a free version. The Pro version isn't expensive and provides more reporting features.

Before begining a study outside, it helps to get a lay of the land. What does your neighborhood look like? What does it contain - rocks, plants, animals, attractions, hazards, streams, hills... outcroppings, 

A Snowy Interlude

We haven't had a lot of snow this winter in the Denver area. A lot of places in the U.S. have had a lot more than they're used to.

Snow is a part of geology, too. It packs pockets in the mountains to form glaciers. The seasonal freezing and thawing allows water to sleep into cracks in rocks and wedge them apart. Earth science includes the study of the solid, liquid and gaseous parts of our planet and they all cooperate to make Earth what it is.

This time, I did a common science hobby activity that I've never done before. I tried first on February 1, when the snow was first packing in, but it was a very fine dust with very little crystal development. On the second day, there were big flakes and I got these photographs.

I took them with a clip-on microscope lens for a smartphone. It has a built-in LED illuminator, which explains the glare. After cropping and sharpening the images, I ended up with these images.

To get the photographs, I caught the flakes on a slide that I had left in our freezer overnight and used the smartphone camera with microscope lens, hand-held, to capture the images. It was quick and sloppy work but easy.

The flakes themselves were from a single sample. Had I spent a lot more time catching more I could have likely come up with better examples, but these are quite good enough to show the varied hexagonal nature of ice.

When taking pictures of snowflakes, the surface you use (in this case, a plastic microscope slide) must be below freezing or the flakes will melt as soon as they land on it. Also, don't use a hot light source like a hot incandescent lamp to illuminate the slide, and don't breathe on the flakes.

Of course, an actual microscope would give you better results, but the scope should also be chilled, perhaps by leaving it for an hour in the place where you will be photographing, and in humid environments, protect the instrument from condensation (cover it and use an eyepiece cap until you're ready to shoot). 

If you use a smartphone camera, you might be able to use a gooseneck camera holder and phone clamp to steady the phone.

Rockd by Walnut Hills

This is going to sound like an advertisement...consider it a recommendation.

Rockd by The Mactostrat lab at the Geoscience department at the University of Wisconsin - Madison is one of my main tools for geological exploration. It's an app on my smartphone. 

Where most geology apps are reference works, like geology textbooks or encyclopedias on your phone, Rockd is equipment. It includes a Brunton compass and information about localities with topographic and geological maps and geology and paleontology profiles. It's pretty impressive how much local information it packs. (The Brunton compass needs a gyroscope and magnetometer to work.)

Let's see what it says about my backyard, Walnut Hills in Centennial, Colorado.

When I open Rockd, I see this, my dash board.

It gives me an overview of my area. 

People that don't live here often mistake Denver for a mountain town. It may be a gateway to the Rockies but it's situated at the western edge of the Great Plains. It's hilly grasslands.

Specifically, Centennial, a town in the Denver metro area, is near the western edge of the Colorado Piedmont region. 

Denver makes a big deal about being the Mile High City but, actually, it's down in a hole carved by the South Platte River. Just about everyone around us is at higher elevations.

We're sometimes called the "high plains" but, technically, the high plains are to the east of us. As explained by Rockd, when I tap the Colorado Piedmont panel, the high plains were formed when the Colorado Plateau was pushed up when the Pacific plate crashed into (and is still crashing into) North America. The Rockies are still growing but erosion is happening faster and the craggy appearance of the Rocky Mountains is due to the deep cutting of millions of years by rain, frost, wind, and chemical action. All the debris that washed out of the mountains piled up to form the high plains, and then streams running from the mountains started cutting the softer sediment down to form the Colorado Piedmont.

How old is the rock around here? Rockd says 0.0117 mA (that stands for "mega annum" or million years) to present. This is fairly new stuff. The late pleistocene began 0.02 million years ago and the Quaternary is the most recent age of geologic time. You probably know that the continents have shifted around a lot in the past. Here's what Rockd says the World looked like in the Quaternary age.

Same as today. Really new stuff.

The colluvium mentioned is "generally unconsolidated material deposited on slopes by gravity and sheetwash". (The original source sited is Trimble, D.E., M.N. Machette, 2003, Geologic Map of the Greater Denver Area, Front Range Urban Corridor, Colorado: U.S. Geological Survey Geologic Investigations Series 1-856-H.

(If I poke the citation, Rockd carries me to the actual paper.)

The layer of colluvium is generally more than 1.5 meters thick. Mind you, that's our bedrock. Above that is the regolith. Regolith is the term for the bedrock after it rots. We have a lot of debris under our feet..

It's sort of hard to tell if the stuff in the Little Dry Creek stream bed is native or if it was placed there to slow erosion, or if it has been washed down from architectural fill upstream, but it could easily be part of the colluvium washed out of the mountains long ago. Some of that is pretty chunky.

So, we're at 5732 feet. Littleton is right on the river at 5351 feet. We're situated right at the top of the rim of the South Platte River valley, which makes the valley 381 feet deep here. The river comes out of the mountains due west of both us and Littleton at Waterton Canyon. Water flows downhill so Denver, through which the South Platte flows is lower in elevation at 5130 feet (Wikipedia says 5139-5690 feet but that would be the whole Denver metro area.)

Here's a geologic map of the area from Rockd.

The lighter stuff is the colluvium I've been talking about. The darker is Dawson formation which is an older Late Cretaceous to Paleocene rock...100.5-56 million years old. It might be worth visiting the next neighborhood over to see if Willow Creek digs into that sandstone.

Most of the fossils listed in this area are nearer the bottom of the river valley, so I don't expect to find any in this neighborhood (though I will look for some microfossils in the creek bank), also most of the minerals will be clays and quartz since most of the other stuff would have broken down long ago.

Rockd is a free download, so install it and see what it has to say about your area. You might be surprised.

Walnut Hills

Be forewarned that geology, like astronomy, and paraphrasing Gershwin, is a sometimes thing. Weather, hydrology, and economic factors and play havoc with your plans. That said, I always encourage lifelong learners to explore close to home first. That's the easiest and most accessible focus and everyplace is interesting.

My geology laboratory will be the Little Dry Creek valley in the Walnut Hills neighborhood in Centennial, Colorado. I have been assured that there is, in fact, not a single walnut tree in Walnut Hills. Also, I have never seen Little Dry Creek without water flowing through it. And it is "little" not because of it's size. It was named after the same engineer from New Hampshire, Richard Sullivan Little, that Littleton, Colorado was named after. Little settled in the area with his family in 1862. The town of Littleton is about 15 miles due west of Walnut Hills.

Two creeks have sculpted the Walnut Hills area, Little Dry Creek and Willow Creek. The soil is deep and soft so the creek valleys are fairly deep and steep. They are tributaries of the much larger South Platte River valley in which the Denver metro area is located.

This is a view of Little Dry Creek from Uinta Street in the Walnut Hills neighborhood where it flows behind Walnut Hills Elementary School. The hilliness is directly due to the erosive action of the creek.

The creek begins as runoff from the area just east of Walnut Hills and is tracked by the Little Dry Creek Trail, part of the Centennial Connector Trail, which parallels it throughout the neighborhood. I take the trail often on trips to the several shops in the area, so I have plenty of opportunities to study the area.

In general, road cuts, newly graded dirt roads and other architectural features that clear dirt off the rock below are a geologist's friend...not necessarily here.

It is an urban area, which means that I will have to be careful to distinguish between the actual geology and landscaping. Granite is not indigenous to this area so the rocks in the above photo were brought in. Here is a picture of the natural materials that inhabit the area.

The dirt and mud goes pretty deeply.

That doesn't sound too interesting, geologically, but I think you'll find that not to be the case. The place in the photo is at the western border of the neighborhood and is the only place on Little Dry Creek that shows a well defined soil profile, so I will certainly be coming back here.

On a walk down the trail to a local grocery, I used my AllTrail app to get an idea of the shape of the valley. I started at the eastern border of the neighborhood and walked to the western border. Here's the map and elevation profile.

Over 1.2 miles, the creek drops about 130 feet. Of course, this is the elevation profile of the trail, but the trail begins and ends at close to the elevation of the creek. The grade is pretty much linear. The hump at mile 0.6 is where the trail runs up the shoulder of the valley above the creek. 

On the return trip, I walked up the main road and cut down Uinta for a cross section of the valley down from the rim. Here's an elevation profile of that.

I'll take some other cross sections later. Of course, they change from the top of the valley to the bottom. There are five places that roads cross the creek on the neighborhood. 

Notice above that AllTrails provides topographic maps. The gray lines in the above maps are contours. Google Maps, Google Earth and the Rockd app also gives you topographic maps. When hiking, a topographic map is important. When exploring the geology of an area, they are necessary. A topographic map shows you the shape of the land.

Rockd also provides geological maps of areas. Those show you the kind of rocks and history of an area. I'll look at what the Rockd app has to tell me about Walnut Hills in the next blog.

It's possible that you have been walking around your home territory for years without considering what's under your feet. The next time you're out, look around and ask yourself how the land became the way it is. What were the shaping forces? What are the rocks and dirt like and why are they like that?