Grand Canyon Geomorphology_ What is First is Last__ GPH 112_ Intro to Phys Geography Lab.pdf

Grand Canyon Geomorphology: What is First is Last? Due No due date Points 7 Questions 7 Time Limit None Instructions from https://www.smbc-comics.com/comic/strata (https://www.smbc- comics.com/comic/strata) The events that shaped the geomorphology of the Grand Canyon can be ordered (called relative dating) from oldest to youngest. Sequencing what you are seeing is a great first step to sorting out the geomorphology of this landscape. We need to stress to you that we are not trying to trick you with questions that look and seem easy. That is not our way. We want you to kick back and enjoy learning about the Grand Canyon. Tricking you is antithetical to this goal. So if something seems super obvious to you - great. That means you are a "natural" in thinking like a geomorphologist.

We assume that all of this material is pretty new to you, even though we ho this material in your physical geography lecture. But if not, the questions will rete There are lots of sedimentary layers of Mesozoic age that used to be on top of th these strata by visiting areas north of the Grand Canyon, such as Bryce and Zion illustrated below from http://geologylearn.blogspot.com/2016/03/the-geologic (http://geologylearn.blogspot.com/2016/03/the-geologic-column.html)

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Attempt Score for this quiz: 7 out of 7 Submitted Jan 29 at 12:52pm This attempt took 19 minutes. 1 / 1 pts Question 1 This question focuses on an idealized geological cross-section in Grand Canyon region, that includes nearby Bryce and Zion National Parks, as illustrated below from http://geologylearn.blogspot.com/2016/03/the- geologic-column.html (http://geologylearn.blogspot.com/2016/03/the- geologic-column.html) (http://geologylearn.blogspot.com/2016/03/the- geologic-column.html) The basic idea of a cross-section is to portray a vertical sequence of rocks. Geologists use a concept called "superimposition" where sedimentary rock layers (called strata) on the bottom are the oldest. Whatever goes on top has to be younger.

The Grand Canyon's sedimentary strata (layers) starts with the Cambrian period and ends with the Kaibab Limestone in the Permian period -- all within the Paleozoic era. Way down deep in the Grand Canyon are rocks that are much older, forming in different eras in the Precambrian. Zion National Park's strata is mostly Triassic in age, while Bryce National Park's strata include all periods in the Mesozoic (Dinosaur) era and even afterwards. HINT: as you look at the diagram, think of the cartoon at the start of this lab. The process of superimposition is what drives thinking about the relative ages of rocks. Layers (strata) deposited at the bottom of a sequence must be older than the strata deposited on top. And, other sorts of rocks (e.g. those metamorphic and igneous rocks at the bottom of the

Grand Canyon) that underlie the lowest strata must be older that that lowest strata layer. QUESTION: Where would you go to see the oldest rocks in the region and then the youngest rocks in the region? Please answer the question based on the diagram above. Think simplistically. If you are quite familiar with the geology in the region, you could be clever and answer that there are very young (1.2 million year old) lava flows down at the bottom of the Grand Canyon. But please don't think at a higher level than a 100-level basic science course. oldest: bottom of the Grand Canyon; youngest - middle of the Grand Canyon oldest: bottom of the Grand Canyon; youngest - Zion National Park youngest and oldest both are found in ryce National Park oldest: bottom of the Grand Canyon; youngest - Bryce National Park Correct! Correct! Correct! Correct! This is the clearest and best answer: oldest: bottom of the Grand Canyon; youngest - Bryce National Park. 0 / 0 pts Question 2 Geologists love a feature you can see in the Grand Canyon called an unconformity -- a concept that means no rocks were deposited during a period of time. Instead, erosion was going on instead. Perhaps the most famous unconformity in the world is "the Great Unconformity" -- seen in cross-section and in a photo. Its considered "great" because it is seen so beautifully in the Grand Canyon, because it represents a very long period

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