Elma under the Sea
this area was covered by a broad, shallow sea
What is Elma/Grays Harbor area
What causes tectonic plates to move?
Mantel convection
How did volcanic ash get into the rocks from Porter
Ash from volcanic eruptions drifted over sea and settled and sank into the water,
What was formed around Elma from the tectonic forces squeezing and folding the rocks?
The Willapa hills
As sediments piled up, pressure squeezed out _______ and compacted the layers.
water
How was the Elma area lifted above the sea floor and folded into hills?
Plate collision between Juan de Fuca plate and North American plate.
The Juan de Fuca ridge is formed how?
By two plates pulling apart
Fossils in the rocks from Porter are from what type of species? Name one.
Snail, mollusk, clam
How does sediment form from the hills?
Eroding rocks from rain and ice and streams.
Rivers like the _______ began cutting valleys into the new hills.
Chehalis
What evidence exists that this area was once under the sea?
Marine fossils in the rocks
What is geologic feature is formed at the boundary between the Juan de Fuca plate and the North American plate.
Cascadia trench
Where did the sediment that forms the porter rocks come from?
mud and silt carried into the ocean by rivers, and ash carried by the wind.
How does the sediment get to the sea?
It is carried by streams.
Along Highway 12 near Porter, cliffs expose ancient _______ beds.
sea
What type of rocks are the Porter rocks that contained 35 million year old marine fossils?
Sedimentary rocks
What is happening at the Cascadia trench?
The Juan de Fuca plate is subducting beneath the North American plate.
How old are the Porter Rocks approximately?
35 million years old
What is lithification?
The process where sediment is turn into rocks by pressure and cementation by minerals.
1. As the Juan de Fuca Plate descends, it releases _______ into the mantle, causing melting.
steam
What is cibicides elmaensis?
A microscopic marine fossil
How does subduction lead to volcanic eruptions?
When subducting plate is pushed deep into the mantel, the crusts melts and magma and steam rise to the surface.
What turned the sediment into rocks?
Pressure from being buried and minerals glued the sediment together to form a rock.
Describe the feedback loop of sediment and rocks created by the tectonic forces
land lifted out of sea and folded into hills, hills erode and sediment carried into sea, new rocks form on as sediment is buried deep and cemented together, and plate collision lifts and fold land into new hills.
2. Rising magma fueled the ancestors of volcanoes like Mt. Rainier, Mt. Adams, and Mt. _______.
St Helens