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COLTON

GRIZZLY PEAK BL.

SKYLINE

BL.

SHEP

HERD

CA

NYON

DR.

DR.

SNA

KE RD.

SARONI

HOMEGLEN

LN.

RD.

OLD TUNNEL ROAD

GRIZZLY TERR. DR.

THO

RND

ALE D

R.

DR.

THO

RNHILL

HEATHER R

IDGE

WAY

24

SKYLINE BL.

PINEHURST ROAD

SKYLINE BL.

OLD TUNNEL R

D.

EVERGREEN

AVE.

SKYLIN

E BL.

FISH RANCH ROAD

TU

NNEL RD.

SKYLINE BL.

SKYLINEBL.

24

PINEHURST ROAD

BAY AREA RIDGE TRAILSKYLINE TRAIL

HUCKLEBERRY PATH

TRAILPHILLIPS

TRAILVOLCANIC

STREA

M TRAIL

POND TR.

VOLC

ANIC TRAIL

QU

ARRY RD.

QUARRY TRAIL

WEST RIDGE TRAIL

OVERL

OOK

TRAIL

LOW

ER

PINEHURST TR.

SKYLINE TRAIL

BAY AREA RIDGE TRAIL

SKYLINE TRAILBA

Y AREA RIDGE TRAIL

ROU

ND

TO

P LO

OP

TR

AIL

ROUND TOP LOO

P TRAIL

McC

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Loop

Trai

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.29 miles to Fish Ranch Road.1.75 miles to Tilden Reg. Park

.18 .20

.51

.06

1.36

Round Top Creek

San Leandro Creek

EBMUD WATERSHED.Hiking permit requiredexcept when hiking onSkyline Trail/Bay AreaRidge Trail. Call (510) 287-0459.

HUCKLEBERRYBOTANICREGIONALPRESERVE

REDWOOD REGIONAL PARK

HuckleberryStaging Area

Water Tank

Round Top1,763

Quarry Pit

Private

Property

SibleyStagingArea

AC Transit #305

Fire St. #6

GRIZZLY PEAK OPEN SPACE

SIBLEYVOLCANICREGIONALPRESERVE

DOGS MUST BE ON LEASH

from park boundary to

Sibley staging area on Skyline Bl.

TO MONTCLAIR

EBMUDEBMUD

To Walnut Creek

Quarry Pit

O A K L A N D

Separate map available.

Separate map available.

SkylineGate,RedwoodReg. Park

Old Tunnel RoadStaging Area

SibleyBack packCamp

SIBLEYVOLCANICREGIONALPRESERVE

Self-guided tourbegins here. See descriptions below.

CALD

ECO

TT

TUN

NEL

DOGS AND HORSES ARE NOT PERMITTED IN HUCKLEBERRY except passing through on the

Skyline National Trail.DOGS MUST BE UNDER VOICE

CONTROL AT ALL TIMES.HORSES MUST STAY

ON THE SKYLINE TRAIL.

BICYCLES ARE NOT PERMITTEDIN HUCKLEBERRY

REGIONAL BOTANIC PRESERVE.

WilcoxStationStagingArea

Best access to the staging area is from Canyon Road in Moraga, then turn right on

Pinehurst Road.

AREA IN YELLOW SUBJECT TO CLOSURESee www.ebparks.org/

sibley for status.

NO ACCESSBEYOND GATE

NO ACCESSBEYOND GATES

To Canyon Road and Moraga

FENCELINE

FENCELIN

E DOGS ARE NOT PERMITTEDIn this section of parkland.

6 parking spots

7 parking spots

38 parking spots

14 parking spots

10 parking spots

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5

6789

1011

LEGEND Hikers, Horses & BicyclesHikers & HorsesSymbol denotes Skyline Trail /Bay Area Ridge TrailHikers OnlyMileage Between PointsPaved RoadParkingRestroomsVisitor CenterDrinking WaterInformation PanelBackpack CampSelf-Guided Tour StopsGate, No Vehicle Access

.28

Contour Interval 10 feet

North

Rev.

7/1

7

0 3/8 Mile1/41/8

4

A B C D E F G H I J K L

4

1

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A SELF-GUIDED TOUR OF ROUND TOP VOLCANOESBy Stephen W. EdwardsFormer Director, Regional Parks Botanic Garden

This Preserve features a complex volcanic center that was the source, 10 million years ago, of most of the lavas that underlie the ridges from Inspiration Point in Tilden Regional Park to Moraga. Round Top stands out today because it was originally surround-ed by sedimentary rocks of the Orinda Formation, which have eroded away. Over the years, folding and erosion have exposed a cross section of a volcano.

Lava from the vent has been dated as old as 10.2 million years. Round Top’s basaltic dikes (feeders of the vents), tuff-breccias (ash containing a jumble of blocks and chunks of lava), lava flows, red-baked cinder piles, air-fall tuffs, and the major vent itself can all be seen in an easy hike. The numbered descript-ions below correspond to stops along the trail.

Walk up the paved road to the EBMUD water tank to see a dark basalt dike, a feeder of lava to the crater, that cuts through a sequence of tuff-breccias (grayish brown) and pebbly mudstones (light gray), inside and near the crater bottom. This pit was made by quarry operations in which massive basalt lava was removed. The pit exposes the interior of the Round Top volcano. You are stand-ing on bedded tuff-breccias, which filled much of the crater, settling at times into a small lake. The steep wall across the pit consists of lava that capped the crater after it was filled. Eventually the Round Top vent buried itself in basalt flows.

This roadcut exposes Orinda Formation river gravels, sands, and mudstones. The red (when moist) streaks and layers in these river beds were

caused by oxidation of iron in the sediments. Such varicolored “redbeds” sometimes contain fossils of plants and animals. Elsewhere in the Preserve, bands of more intense red are found at the tops and bottoms of lava flows, where iron was oxidized and reddened by baking and steam action; these bands are called “bake zones.”

Before you is a wall with basalt on the left and Orinda mudstones on the right. The bedding in the mud-stones gives the appearance of drag-folding resulting from relative uplift of the lava occurring during the past 10 million years. Alternatively, the disruption of the mudstones may have occurred earlier, at the time of volcanic activity. This site was close to, or was in, the wall of the volcano, and would have been subject to slumping, sliding, and plowing.Continued on reverse

Year opened: 1936 Acres: 928Highlights: Hiking, biking, horseback riding, self-guided interpretive tour, backpack camp, panoramic views.Did you know? This parkland was opened as Round Top in 1936 with the formation of the Park District. It was renamed in 1972 to honor Robert W. Sibley, a Park District founder and director.

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