However, to make sure that we understand relative motion on faults, we will use half-arrows on each side of any fault in the cross-sections. The worksheet, which is separate, contains a different set of detailed questions that you will answer and turn in. Question 10 2 points : On the South Half, we can also notice that many faults have occurred in the area of the Cheops Pyramid. Profiling is also covered in the event. Reverse and thrust faults are the result of compressional deformation; large scale examples of both are found in mountain ranges that formed at convergent plate margins such as the Appalachian, Ouachita, and parts of the Rocky Mountains. Now let's practice on a couple more imagined cross-sections: Question 4 3 points : What is the sequence of events that can be inferred from the above cross-section? This forms a dome-like structure. The first one if fairly straightforward, while the second and third cross-sections are generally more complex.
The solution to this example problem, which may be found on the internet, shows the principles and reasoning behind it. You are also encouraged to use Illustrator or Inkscape to draw your cross section. Faults are fractures or breaks in rock along which movement has taken place. Each rock layer was deposited at a different geologic time. To review our principles of relative dating as applied to such geologic cross-sections, we will make use of a neat learning tool available on the Internet. A normal fault is when the hanging wall has moved down the fault plane, in concert with gravitational forces.
Abrupt breaks and shifts that occur along faults in the rocks are the source of earthquakes, a topic for another day. Question 11 2 points : Pinpoint the time at which this tilting took place. Below is a diagram explaining strike and dip. Faults Refer to the Geologic Structure Basics page section on. The maps Basics page includes an introduction to the Basics Table of. The map legend is on the complete geologic map of Washington state that you can open by clicking on the link at the beginning of this section.
See the link above to open the complete map. Construction problems require students to draw their own cross sections, use a topographic map to create a profile, use or create a stereonet, etc. As the architecture of the earth, geologic structures form the mountains and basins of a landscape, determine geologic hazards such earthquake and landslide zones, and control the location of geologic resources in the crust. Finally, students may need their for parts of the lesson a document used widely in the New York State Earth Science Regents course as well. Click to access the activities related to the interpretation of geologic sequences.
In some cases, rocks bend - undergo slow, solid-state flow - and are folded. Think about how these relationships might be portrayed beneath the surface. Refer to the for a reminder of what constitutes a well-performed lab. We could draw such a profile across several miles of landscape so we would see a side-view of the land's surface over which we might be hiking. There are many types of unconformities.
What principle s of relative dating did you use in order to arrive at your interpretation of the relative timing of each event? To understand a stereonet, consider an imaginary sphere hanging above a flat plane which is where the stereonet is drawn. Dip-slip faults, and the sense of movement, can be determined on a geologic map if the dip of the fault plane is known. If you would need to access the resource in its entirety in a Word document, you can do so here:. The dip of a fault is the perpendicular of the strike. In the same way, such a transect could also show the inferred profile of the geology underfoot -- the expected rock layers and structures beneath the land from the northwest corner to the southeast corner of the map.
In that case, the inclination in the cross section view is something less than the true dip and is called the apparent dip. Cross-sections seeing beneath the map To take a real-world look at geologic structures and how they appear on geologic maps, we will use the geologic map of Washington State published by the Washington State Department of Natural Resources. The Geology of the Grand Canyon: Shown below is a real transect across the entire Grand Canyon in two parts. Folds Refer to the Geologic Structure Basics page section on. You can also determine the relative geologic history of the map area using another geologic principle, The Law of Cross-cutting Relationships, which states that any geologic feature which cuts across another is the younger of the two features. Last updated by Michael Leite 2014-10-15. Determining the subsurface geologic structure will require some interpretation of the map, including recognizing patterns on the surface that indicate the attitude of different rock layers, paying attention to various map symbols that provide relevant information, and using a correlation chart to determine stratigraphy.
They represent a long-standing contribution to geology. This event tests competitors' knowledge of structural geology, geologic history, map reading, and related topics. Also an igneous intrusion is present labeled T and a fault is present labeled A. They will help prepare you for completing the worksheet. If the hanging wall moves down in reference to the footwall, the fault is called a normal fault. Which unit would be listed at the bottom of the sequence? Mark the cross section line on your map.
Fault-bounded structures Refer to the Geologic Structure Basics page section on. The number of each question below corresponds to the questions on our submission form for this week's lab assignment. This often exposes previously subterranean rocks on the surface, allowing the natural processes of weathering and erosion to take place. An unconformity, in general, is a gap in the geologic record of a region. The map legend comes in handy to match the color of a rock unit with its label.