American Lake

Mason Lake

S. F. Skokomish River

N. F. Skokomish River

Black River

Elwha River

Dungeness River

Dosewallips River

Duckabush River

Hamma Hamma River

Vance Creek

Nisqually RiverDeschutes River

Kennedy CreekSkookum Creek

McLane Creek

Puyallup River

Carbon River

South Prairie Creek

White River

Green River

Cedar River

S. F. Snoqualmie River

M. F. SnoqualmieRiver

N. F. Snoqualmie River

Scatter Creek

Skykomish River

S. F. Tolt River

N. F. Tolt River

Sultan River

S. F. Stillaguamish River

Sauk River

Suiattle River

Snohomish River

Duw

amish Waterw

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Lake

Was

hing

ton

Lake

Sam

mam

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LakeTapps

Lake Cushman

Lake Kapowsin

Tanwax Lake

Ohop Lake

Black Lake

Lake Youngs

Dow Mountain

Cougar Mountain

Tiger Mountain(above glacial ice)

SnoqualmieFalls

Green Mountain

Gold Mountain

Ediz Hook

Dunge

ness Spit

Lemon Hill

Jones Hill

Pinnacle Peak

Spar Pole Hill

Sugarloaf Mountain

Fuller Mountain

Haystack Mountain

Devils Butte

White Star

Dayton Peak

Mount Turner

Mount Walker

Mount Zion

Lookout Hill

Ned Hill

Round Mountain

McDonald Mountain

Striped Peak

Seattle

Tacoma

Olympia

OakHarbor

Port AngelesSequim

Bellevue

Everett

PortTownsend

Sammamish

IssaquahPort Orchard

Bremerton

Edmonds

Sea Tac

Federal WayAuburn

Sea Tac

Renton

Kent

Marysville

Lakewood

Redmond

Shoreline

Lynnwood

Kirkland

Lacey

Puyallup

Bothell

Burien

UniversityPlace

DesMoines

Lake Stevens

Maple Valley

Kenmore

Mukilteo

Mountlake Terrace

Tukwila

Mill Creek

Arlington

Covington

Bonney Lake

Tumwater

Monroe

LakeForest

Park

Woodinville

Snoqualmie

Enumclaw

Newcastle

Shelton

Sumner

Edgewood

Poulsbo

Fife

Snohomish

Dupont

Gig Harbor

Milton

Yelm

Orting

Duvall

Pacific

Tenino

SkokomishIndian

Reservation

SquaxinIndian

Reservation

StillaguamishIndian

Reservation

SnoqualmieIndian

Reservation

MuckleshootIndian

Reservation

NisquallyIndian

Reservation

PuyallupIndian

Reservation

TulalipIndian

Reservation

Sauk SuiattleIndian

Reservation

Port Madison - Suquamish

IndianReservation

Port Gamble - S’Klallam

IndianReservation

JamestownS’Klallam

IndianReservation

Lower ElwhaKlallamIndian

Reservation

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McNeilIsland

Fox Island

Harstene Island

Maury Island

VashonIsland

BainbridgeIsland

Whidbey Island

CamanoIsland

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Toan

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Quimper Peninsula

Miller Peninsula

fault

1

2

3

4

5

6

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2

3

4

5

6

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US Highway 101

US Hig

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US Highway 101

US

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US

Inte

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US Interstate 5

US

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US Interstate 90

US Highway 2

0 10 20miles

Co rd i l l e ra n i ce s h ee t

Puget

lobe

N

www.dnr.wa.gov/geology ©2017 Washington Geological Survey

Drumlins - Drumlins (or fluted

ridges) are geologic features where

movement of the ice sheet smooths glacial

sediment into elongated teardrop shapes. Drumlins

align in the direction of the ice flow and are evident across

most of the Puget Lowland.

Mima Mounds - Intriguing features called Mima Mounds are found on

Mima Prairie and in several outwash channels in the southern part of this

map. Composed of organic-rich, sandy soil, Mima Mounds on this map are only

found on the most recent glacial outwash deposits. The origin of the mounds has been

debated for decades and a consensus on their formation has not yet been agreed upon.

Kettles - Glacial kettles are depressions that form when a retreating glacier leaves a bit of ice behind which then

becomes buried by sediment shed from glacial streams. When the block of ice melts, the sediment collapses, forming

a kettle. Kettles can be dry or filled with water, depending on their depth and the level of groundwater in the area.

Eskers - Eskers are snake-shaped landforms that are often found near the glacier’s terminus. Eskers are formed when rivers that are

underneath, on top of, or within a glacier, transport pebble- to cobble-sized gravel that is exposed once the glacier retreats. The resulting landform is a

sinuous ridge of gravel that runs roughly parallel to the direction of ice flow.

Outwash Channels - Dozens of stream channels were created by glacial lake outflows, glacial meltwater streams, and glacial outburst floods. Today, many of the

channels no longer transport water or have smaller streams occupying them than the streams that formed them.

Fault scarps - Sharp breaks in the fluted topography make it easy to identify geologically recent faults, such as this one called the Toe Jam Hill fault on Bainbridge Island west of Seattle, which is

part of the Seattle fault zone.

During the advance and retreat of the Puget lobe, drainages around

the ice sheet were blocked, forming multiple proglacial

lakes. The darker colors on this map indicate lower elevations,

and show many of these valleys. The Stillaguamish,

Snohomish, Snoqualmie, and Puyallup River valleys all once

contained proglacial lakes. There are many remnants of

these lakes left today, such as Lake Washington and Lake Sammamish, east of Seattle.As the Puget lobe retreated, lake outflows, glacial meltwater, and glacial outburst flooding all contributed to dozens of channels that flowed southwest to the Chehalis River

at the southwest corner of this map. Remnants of these

channels can be seen along the eastern and southern edge of the

colored area in the map. Present-day Lake Kapowsin and

Ohop Lake both occupy one of these channels. Today, the Chehalis River flows through a wide valley that

was largely sculpted by ice-age meltwater.

Puget lobe drainage channel

(ice-age Chehalis River)

What is Lidar?The fine detail depicted on this map is the result of lidar. Lidar is a remote-sensing technique that uses light pulses to rapidly collect a very large quantity of elevation points across large areas.To learn more about lidar in Washington visit: www.dnr.wa.gov/lidar

*

During the last ice

advance and retreat (in the latest Pleistocene), an

extension of the Cordilleran ice sheet, called the Puget lobe, covered the Puget Sound region (see location map below).

The colored area of the map (at right) represents the approximate maximum extent of the Puget Lobe during this time period. During glacial maximum, the location of modern-day Seattle (near the center of this map) was beneath 3,000 feet of ice.

All of the land and waterways in this region were shaped, at least in part, by the glacial ice of the Puget lobe. Many large-scale glacial landforms are preserved in the landscape today. In this lidar*-derived map, landforms such as drumlins, kettles, eskers, and glacial stream channels can be seen. Examples of these and other landscape features are enlarged at bottom right.

Most of Washington’s population lives in this region—the glacial geology influences many aspects of daily life, including transportation, water supply systems, agriculture, and building regulations.

Glacial Landforms of thePuget Lowland