Geology of Mount Rainier

14,410 feet high An active volcano that affects the weather, rivers, valleys, and habitats Formed by FIRE and ICE National Park Service Mount Rainier National Park Mount Rainier is:

National Park Service Mount Rainier National Park Mount Rainier is: Highest peak of the Cascade Range

National Park Service Mount Rainier National Park View from South:Mount St. Helens (foreground) Mount Rainier (background) Mount Rainier is:

An Active Volcano National Park Service Mount Rainier National Park Mount Rainier is: Last eruption in 1894

National Park Service Mount Rainier National Park Volcanism

Subduction of the Juan de Fuca plate National Park Service Mount Rainier National Park Volcanism

National Park Service Mount Rainier National Park Stratovolcano – “strato-” indicates layers of flows 90% lava flows, 10% block and ash flow Mostly andesite, some dacite – silica content is between 61 – 64% Viscous lava flow that usually erupts violently, not “flowing” like that of a shield volcano

National Park Service Mount Rainier National Park Images by Pat Pringle Washington DNR Orting

LAHAR Mudflows or lahars are the biggest hazard from the volcano They are created when lava meets… National Park Service Mount Rainier National Park HAZARDS

National Park Service Mount Rainier National Park Volcanism… …and Glaciation

National Park Service Mount Rainier National Park Volcanism… …and Glaciation

What’s a Glacier?  A glacier is mass of ice that shows evidence of movement, or “flows”.  25 named glaciers on Mount Rainier  More ice than all other Cascade volcanoes combined National Park Service Mount Rainier National Park

Largest surface area: Emmons (4.3 miles 2 ) Lowest Terminus: Carbon (3,600 feet) Deepest Ice: Carbon (700 feet) National Park Service Mount Rainier National Park

How are Glaciers Formed? Snow accumulation > ablation Snow compresses The mass of ice is called a glacier when it begins moving downhill National Park Service Mount Rainier National Park

How Lava Flow Ridges are Made  During the Pleistocene (“Age of Ice”), glaciers on Mount Rainier were much more voluminous than they are today.  Glaciers filled all of the valleys on the mountain National Park Service Mount Rainier National Park

How Lava Flow Ridges are Made  Lava flows on the path of least resistance  On Mount Rainier, lava flowed along the sides of the glaciers  Lava flows piled on top of each other National Park Service Mount Rainier National Park Ridge-Capping

How Lava Flow Ridges are Made  Over time, glaciers slowly melted  This exposed the ridges created by old lava flows  There are 23 ridges visible on Mount Rainier National Park Service Mount Rainier National Park Ridge-Capping

National Park Service Mount Rainier National Park Take Home Points Lava builds ridges, glaciers carve valleys – together they shape a unique landscape Mount Rainier influences processes both within and beyond the park boundary An active stratovolcano

National Park Service Mount Rainier National Park that’s all

National Park Service Mount Rainier National Park References Driedger, Carolyn. U.S. Geological Survey. Answers to Commonly Asked Questions about Mount Rainier Glaciers, 2008 Seasonal Training Notebook, Mount Rainier National Park. June Frequently Asked Questions, 2008 Seasonal Training Notebook, Division of Interpretation at Paradise, Mount Rainier National Park. Geology of Mount Rainier, National Park Service, U.S. Department of the Interior Seasonal Training Notebook, Mount Rainier National Park. ”Geology Overview”. G:\Education\Curricula\Mountain Geography & Cultures Curriculum\Fuji Rainier lessons 2008\Geology Overview.doc. Revised July 9, Lescinsky, D.T. and Sisson, T.W. “Ridge-forming, ice-bounded lava flows at Mount Rainier, Washington”. Geology: April 1998: v. 26: no. 4: p : 6 figures. Primary Interpretive Themes, 2008 Seasonal Training Notebook, Mount Rainier National Park. Sisson, Tom. U.S. Geological Survey. Mount Rainier’s Geology, 2008 Seasonal Training Notebook, Mount Rainier National Park. Some slides and text taken from “NPS_05” by Tom Sisson, “VolcanoesRockGREEN” by Jennifer Ledenican, and “Living with a volcano in your backyard” by Christina Hamilton.