Morrow Mountain Virtual Field Trip
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School
Johns Hopkins University *
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Course
0031
Subject
Geology
Date
Apr 3, 2024
Type
docx
Pages
3
Uploaded by CountField5348
Morrow Mountain Virtual Field Trip
1.
The Pacific Northwest of the United States is the same tectonic setting as Morrow Mountain was back when the volcanoes were active. What kind of plate boundary is this?
The tectonic setting of the Pacific Northwest of the United States resembles that of Morrow Mountain during its volcanic activity. This area is characterized by a convergent plate boundary, where the Juan de Fuca Plate converges with the North American Plate. This collision results in subduction, with the denser oceanic plate being forced beneath the continental plate. As a result, the region experiences volcanic activity, leading to the formation of the Cascade Range volcanoes, such as Mount St. Helens and Mount Rainier. These volcanoes were once active like Morrow Mountain, indicating a similar tectonic environment.
2.
If the foliation on rock is running north-south what direction is the tectonic pressure
coming from (be specific)?
If the foliation on a rock appears to run north-south, it indicates that the tectonic pressure is likely originating from an east-west direction. This implies that the rock has undergone compression perpendicular to the foliation's orientation. The horizontal force applied during tectonic activity leads to the alignment of minerals within the rock, resulting in the observed north-south foliation pattern.
3.
Give the rock I examined in the parking lot a name that is closest to the names of metamorphic rocks we learned. It’s foliated with a flat surface that is just a little bit shiny from the growth of the mineral Mica. Note- I never say the name of this rock in the video you need to look at your metamorphic rock identification grid from module 1 to give it a name.
Based on the characteristics, the rock you examined in the parking lot appears similar to phyllite,
a type of metamorphic rock. Phyllite typically exhibits a foliated structure with a slightly shiny appearance due to the presence of mica minerals like muscovite or biotite. The foliation in phyllite is discernible but not as pronounced as in other metamorphic rocks like schist or slate. This aligns well with your observations of a foliated rock with a subtle sheen from mica mineral growth.
4.
What does it mean when a geologist says a rock is floating? Should you take orientation measurements on the float?
When a geologist describes a rock as "floating," it means that the rock is not in its original geological context but has been transported to its current location by natural processes like erosion or glaciers. In such cases, the rock may not match the surrounding bedrock.
Taking orientation measurements on a floating rock might not yield accurate results because its original orientation could have been altered during transportation. Therefore, while examining the composition and characteristics of the rock can offer insights into the area's geology, orientation measurements may not be reliable indicators of the region's structural features.
5.
Why are underfit streams so common in the southern United States?
Underfit streams are common in the southern United States due to specific geological and hydrological conditions. The region's geological history, characterized by minimal tectonic activity and gradual landforms, contributes to the development of broad, shallow river valleys over time. Moreover, the humid subtropical climate of the southern U.S. results in ample precipitation and relatively low evaporation rates. This climate fosters the formation of meandering streams with expansive floodplains capable of accommodating significant water volumes, especially during periods of heavy rainfall. Human activities like deforestation, urbanization, and agriculture further disrupt natural drainage patterns, leading to increased sedimentation and exacerbating the prevalence of underfit streams in the region.
6.
In Medieval times a ruler told the peasants that they were free to take anything from the forest that had fallen, branches, trees, leaves, etc. But they were not to take
any live-standing trees. Within a few years, the forest was dying. Why? (that is a true story btw).
The forest likely deteriorated due to unsustainable harvesting practices prompted by the ruler's decree. Allowing peasants to freely gather fallen branches, trees, and leaves depleted essential resources needed for the forest's health. While fallen debris aids in nutrient cycling and ecosystem stability, excessive removal disrupts this balance. Without adequate organic matter replenishing the soil, nutrient levels decline, hindering new plant growth and overall forest health. Furthermore, the removal of fallen material exposes the forest floor to erosion, compounding soil degradation. Ultimately, the uncontrolled harvesting led to the decline and eventual demise of the forest ecosystem.
7.
The area we visited was originally volcanic but the rocks we saw were metamorphic.
What future geological event on the east coast of the US likely provided the heat and
pressure to metamorphose the rock we saw? (hint- there is a HUGE mountain range
that runs up the Eastern US and even over into the UK)
The rocks in the area we visited, originally volcanic, likely underwent metamorphism due to the Appalachian Orogeny, a major geological event in the eastern United States. This mountain-
building process, which occurred around 480 to 320 million years ago, resulted from the collision of tectonic plates. The immense pressure and heat generated during the orogeny caused the volcanic rocks to undergo metamorphic changes, forming the metamorphic rocks we observed. This explanation aligns with the geological history of the region and the known effects
of the Appalachian Orogeny on rock formations along the east coast of the US.
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