Title: Causes of Earthquakes Brown 24-25
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# Causes of Earthquakes 1. Plate boundary interactions 2. Volcanic eruptions 3. Nuclear detonation 4. Meteor impact 5. Dams/Mining/Fracking
Top 5 Causes Plate Boundary Interactions
Learned about this in the previous plate tectonics unit Volcanic Eruptions
As magma rises towards the surface during a volcanic eruption, it exerts pressure on the surrounding rocks, causing them to crack and shift. Nuclear Detonation
Castle Bravo test - largest U.S. nuclear detonation that took place on March 1, 1954, at Bikini Atoll in the Marshall Islands.
The device was expected to yield 4 to 8 megatons, but the actual yield was 15 megatons.
1,000 times more powerful than the atomic bomb dropped on Hiroshima.
The mushroom cloud reached a height of 25 miles and spread over an area more than 25 miles in diameter in less than 10 minutes.
The explosion created a crater on the ocean floor with a diameter of 6,500 feet and a depth of 250 feet.
The explosion vaporized two islands and part of a third Meteor Impact
Think back to what we learned about during the astronomy unit about the Chicxulub impact crater in the Yucatan Peninsula of Mexico.
Asteroid 6 miles wide and traveling at ~45,000 mph hit earth.
Impact released 10,000 times more energy than if all of the nuclear weapons ever created were exploded at same time.
~2,000 nuclear weapons have been tested globally since 1945
Crater ~125 miles wide is created.
An impact like this will fracture the surrounding rock and create many faults. Dams/Mining/Fracking
From the How Humans are causing Earthquakes reading homework assignment U.S. Earthquake Hazard Map - 2008 U.S. Earthquake Hazard Map - 2014 U.S. Earthquake Hazard Map - 2018 U.S. Earthquake Hazard Map - 2023 U.S. Earthquake Hazard Map Analysis
1) Where are the highest hazards in the US? 2) What is the risk level in Massachusetts? 3) What new places have increased in risk over the last 15 years? 4) Why do you think risks/hazards have increased? Hydraulic Fracturing - Fracking Cape Ann Earthquake of 1755
6.0-6.3 magnitude
Biggest in colonized Boston History Luckily were not on a plate boundary...
Stress affects entire plate, not just boundary
Ruptures and movement occur on weak zones Its Our Fault: Bloody Bluff Fault
Located between Concord and Lexington in Minute Man NHP
Bloody Bluff Fault named for the revolutionary skirmish there
Nashoba: hill that shakes