One of the first things I do in my introductory geology class is talk about the structure of the Earth. Knowing the names, composition and physical properties of the different layers is an important foundation for the rest of the course, which means I fret about presenting the information in a clear and memorable manner*. This year, I decided to try a slightly different approach to in the past: I started my lecture by drilling an imaginary borehole down into the Earth from our lecture room. We discussed how what we were drilling through changed as we crossed the Moho, the lithosphere-asthenosphere boundary and the core-mantle boundary, and then crossed them again as we came up at the antipode of NE Ohio, which lies in the Indian ocean off Australia. Rather conveniently, this meant I had a good opportunity to discuss the differences between oceanic and continental lithosphere. It seemed to work pretty well. This is what the board looked like at the end of my lecture:
The whiteboard following my Earth Structure lecture. I ended up having to move a table which restricted my access to the right hand side of the board in the middle of the lecture. I’m sure my class thought this was very amusing.
I gave the students blank cross-sections to fill in with all the information as we went, but then I thought that maybe I could give my students an even better study resource. I took the rough figure I had created in Inkscape to work out how to arrange all the information in the cross-section, spruced it up and added text boxes explaining all the most important information, and voilà:
The Earth, Down From Kent, Ohio. Click here for a large version.
I think it turned out pretty well. Anyone who finds this useful is welcome to use it with attribution; if you want the .svg file so you can modify it to fit your location, get in touch.
*a constant worry for most of the course, to be honest.
As the US National Park Service celebrates its Centennial this year, we thought we’d celebrate with it by sharing some of our favorite photos from the national parks we have visited in the era of digital photography.
Congaree National Park
Hydrogeology students measuring streamflow and groundwater levels in the midst of a very impressive floodplain forest.
Crater Lake National Park
Wizard Island, a volcano within a volcano.
The hydrologist very much enjoyed seeing the USGS lake level gage perched above Crater Lake’s cold, deep water.
Cuyahoga Valley National Park
We are super lucky to have a local National Park, especially one that is free to everyone, all year long. We keep finding new places to explore in this park, but here’s a picture from our most recent adventure.
Anne and Geodog explore the Ritchie Ledges in Cuyahoga Valley National Park
Grand Teton National Park
Grand Teton is very pretty when the cloud base is high…
Anne and Geokid venture into the heart of Grand Teton.
Great Smokey Mountains National Park
Two of our favourite things: water flowing over ancient rocks, Great Smokey Mountains.
GeoKid never takes the boring route. Can’t imagine where she got that attitude from.
Hawaii Volcanoes National Park
Exploring a pahoehoe lava flow.
John Day Fossil Beds National Monument
The fossil rich Blue Basin. Anne’s proud that she spotted a fossil embedded in the rock, and she doesn’t want to think about how many she probably missed in passing.
The Painted Hills unit with its spectacular paleosols is near where Anne went to field camp and is where she went to celebrate defending her PhD (nearly 10 years ago now!)
Mammoth Cave National Park
Spectacular curtain of stalactites, Mammoth Cave National Park
GeoKid finds the going much easier than the adults in a slightly less Mammoth Part of Mammoth Cave.
Olympic National Park
A field trip in Anne’s tectonic geomorphology class in graduate school provided an all too brief glimpse of the Olympics – and a chance to recover from her comprehensive qualifying exams.
So. Much. Wood. On Pacific Northwest Beaches.
Redwood National and State Park
Big trees. Incredibly hard to get a sense of scale in a single photograph.
Fern Canyon is absolutely magical, and absolutely not a place I’d want to be in a rainstorm.
Rocky Mountain National Park
In the valley below, there’s an alluvial fan formed during a catastrophic dam break flood. And behind that there are some mountains. This picture was taken on a Geological Society of America Quaternary Geology and Geomorphology Kirk Bryan field trip, so Anne was in good company ignoring the mountains for the valleys.
Shenandoah National Park
Spectacular columnar basalts (and impressed students), Shenandoah National Park
Thomas Jefferson Memorial
TerraTyke explores the Jefferson Memorial (run by the NPS. Totally counts.)
Yellowstone National Park
The first National Park outing for the Allochthonous family was a 2010 trip to Yellowstone (and Grand Teton). Not a bad starting point.
GeoKid learns that hot springs were worthy of close examination.
Colourful life thriving in hot, silica rich water at Grand Prismatic Spring.
Yosemite National Park
Gorgeous granite galore.
That’s 15 national parks in the last 12 years. More in the pre-digital era. But so many more yet to see. This year, GeoKid is in 4th grade, which means that she gets to take part in the fabulous “Every Kid in a Park” program that gives free park passes to families of every fourth grader. Where should we go next?
On Saturday night, as many people were enjoying an evening out in Maryland, and I was enjoying an evening in in Ohio, a tweet from Johns Hopkins professor and Baltimore resident, Dr. Sarah Horst caught my eye:
I didn't know it was possible for this much water to fall from the sky all at once
She followed up with a video and an offer for people to come whitewater rafting on her driveway. After those tweets, I found a virtual deluge (pardon the pun) of tweets from Baltimore and surrounding residents describing unbelievable rainfall and swiftly rising waters. Soon, reports of people trapped in cars and swiftwater rescues underway began to pour in, from parts of the Jones Falls stream valley in Baltimore and from Ellicott City, 10 miles to Baltimore’s West.
Downtown Ellicott City, in drier times. Photo by Scott Sagihirian used under a Creative Commons license. Sourced from Wikimedia.
Ellicott City is well-known in the Baltimore-Washington area for its historic downtown with a wide selection of shops and restaurants, which would likely have been quite popular on Saturday evening. I remember a fun evening out there a few years after college, when I had a mini-reunion with my roommates.
But this Saturday evening it started to rain. And then it began to rain really really hard. And then the floodwaters began to rise:
This amount of rain in such a short time blows our precipitation records out of the water. (Sorry, the puns just write themselves.) No official records are kept in Ellicott City, but based on nearby records, the rain event has a probability of something like 0.1% in any given year. We often call this a 1000-year storm, but just because it happened in 2016 tells us nothing about whether it will happen again in 2017, so probability is a better way of expressing that. Of course, precipitation records are nowhere near long enough to tell us about 0.1% probabilities, so what can really be said is that this rain event was unprecedented in the 100-200 or so years of records we have for the site.
Being caught in a record-breaking deluge is enough to put a damper on a Saturday evening out, but being caught in that sort of rain storm on Main Street of Ellicott City is a disaster. Ellicott City has the hydrologic misfortune of being located where three streams come together in a narrow valley. The combined stream runs right along the back of Main Street businesses, before funneling into the Patapsco River.
Topography draining to Ellicott City’s Main Street, via Google Maps.
As resdients and business owners begin to clean up from yet another flood, they might be asking themselves a few questions: “Does it make sense to rebuild in a place with such a history of flooding?” That’s a question whose answer depends on economic decisions about acceptable losses in the insurance world and personal and societal decisions about acceptable risks.
Residents, business owners, and insurers might also be asking themselves a science question: “Does our changing climate make events like this more likely?” The short answer is, yes, although attributing the increased chances of any single event to climate change is a complicated business. But there is good evidence that extreme precipitation has increased in intensity over the past few decades, and our climate models suggest that intense rain events will continue to get more intense in the future. That’s because a warmer atmosphere can hold more water vapor, making available more water in the sky when it all comes pouring down on a place like Ellicott City. While the details of exactly where and how much precipitation extremes will increase are still an area of debate, some writers are beginning to describe climate change as weaponizing our atmosphere. Maybe that’s a bit hyperbolic, but people trapped in the floodwaters Saturday night might not think so.
There’s one more thing that likely contribute to Saturday night’s disaster and makes matters worse for Ellicott City now and in the future.
Satellite view of the landscape upstream of Main Street Ellicott City, via Google Maps.
Storm drain receiving urban runoff. Photo by Robert Lawton, used under a Creative Commons license from Wikimedia.
Zooming out on the map shows that the streams flowing downhill to Ellicott City are draining increasingly urbanized areas, where precipitation has no chance of infiltrating if it falls on pavement or rooftops. Instead, rain on these impervious surfaces will be quickly routed to the stream via pipes or drains. Hopefully it makes a stop in some sort of stormwater management structure along the way, but those structures aren’t typically designed for anywhere near this intensity of rainfall. Older developments usually lack stormwater management features entirely. How effectively stormwater management structures can reduce the effects of urbanization on runoff is my area of active research, and to sum the literature up succinctly, what I can say is this: There is not a lot of strong evidence that stormwater management as it has been practiced is very good at reducing peak streamflow at the watershed scale. Instead what we see is that as urbanization intensity increases, so does the size of the flood peak. Bad news for Ellicott City.
So was Saturday night’s flash flood a freak event with a 1-in-a-1000 probability? Was it a symptom of an increasingly extreme climate system? Or was it manufactured by urban land use and inadequate stormwater management upstream? It’s quite possible that it was all three. Further, given the geography of Ellicott City and all of the above factors, a flood like this was an eventual inevitability. It’s just too bad for those who set out to enjoy a night out that it happened to be this particular Saturday night.
Spring semester 2016 is over! Grades were submitted Saturday night, and my research group was eager to get started with our summer research. Since I’m semi-participating in the #365scienceselfies project, I have some fun documentation of our adventures this week.
Students in GEOL 21062, Spring 2016, at Kent State University have been sharing interesting news stories with me all semester long. Here’s our complilation. Hopefully these are interesting things for other people too!