exam Flashcards
(48 cards)
What causes tsunamis at subduction zones?
Subduction zone earthquakes displace large amounts of water, generating tsunamis.
How do tsunami waves differ from wind-blown waves?
Tsunami waves have much longer wavelengths and travel faster and farther.
What happens to tsunami waves when they reach shallow water?
They slow down, increase in height, and become more dangerous.
When do water waves typically break?
When the wave height is about 1.3 times the water depth.
What type of earthquake generally causes tsunamis?
Large, shallow thrust earthquakes at subduction zones.
Why doesn’t swimming help during a tsunami?
The force and debris in tsunami waves are too powerful to survive by swimming.
How do we know about past tsunamis in Japan and the Pacific Northwest?
From sediment records, written accounts, and oral histories.
How many people have died from tsunamis in the past 1000 years?
Approximately 260,000 people.
What does shoreline shaking indicate about tsunami potential?
It may be a warning of an approaching tsunami.
Why does sea level sometimes drop before a tsunami?
The wave trough reaches shore before the crest.
Why is it dangerous to return to shore after a tsunami?
Multiple waves can follow the first, often more destructive.
Why was the 2004 Indian Ocean tsunami so deadly?
Lack of warning systems, high population density, and poor infrastructure.
How does the DART tsunami warning system work?
It uses deep-ocean sensors and buoys to detect pressure changes and send alerts.
What process causes the largest tsunamis?
Landslides, including submarine and volcanic flank collapses.
How do the Hawaiian Islands generate tsunamis?
Through volcanic collapses and undersea landslides.
What is the most likely cause of a tsunami in the Atlantic?
Landslides, possibly from volcanic island flanks like the Canary Islands.
What caused the largest tsunami runup in the past 100 years?
The 1958 Lituya Bay megatsunami caused by a landslide.
Where are different types of volcanoes found tectonically?
Subduction zones, mid-ocean ridges, and hotspots.
Is the mantle a subsurface ocean of magma?
No, it is solid rock that can partially melt under certain conditions.
What causes already hot rocks to melt?
A decrease in pressure (decompression), addition of volatiles, or temperature increase.
What causes hot rock to melt at different tectonic settings?
Decompression melting at ridges and hotspots; flux melting at subduction zones.
Why do hotspot volcanoes form chains?
The tectonic plate moves over a stationary hotspot, creating a chain.
What is the Ring of Fire?
A zone of frequent earthquakes and volcanoes around the Pacific Ocean.
What does viscosity measure?
A fluid’s resistance to flow.
