Field site descriptions

This file contains supplementary information regarding the field sites visited 
during the course of our research.  Access directions for each site, including 
GPS coordinates, are followed by a brief description of the 
colonnade/entablature structures present at that site, and a summary of the 
measurements made at that site.  GPS coordinates are given in degrees (d), 
minutes (') and seconds (''). Sites are identified by a nearby geographic 
feature, and numbered in the order in which they were visited.  The terms 
upper and lower colonnade are exclusively used to refer to columns that 
cooled from the top down, and from the base up, respectively.  The term 
entablature refers to a disordered variant of columnar jointing where the 
columns are usually small, and relatively uneven in their directions.  The 
term fan is used to refer to curving, or splayed, displays of columns, which 
indicate a curving cooling surface (as would occur for lavas emplaced in a 
small valley, for example). These fan features are sometimes elsewhere 
referred to as rosettes, or rock roses.  The relative visual quality of 
colonnades are sometimes indicated by the adjectives well-formed, or 
blocky.  Unless otherwise noted, highway numbers and geographic features 
refer to those in Washington State.

Site 1: Banks Lake I (47d 44' 33'' N, 119d 14' 0'' W), roadside access on 
Highway 155.  Blocky lower colonnade accessed by climbing down east 
from a roadside pullout for a scenic lookout over Banks Lake.  Column 
widths and stria heights were measured on a series of 14 adjacent columns. 
No base of flow is visible, and only the top 2-3 m of lower colonnade are 
exposed.  Cooling direction was determined by plumose direction.  The 
studied colonnade is topped by a thin entablature layer, and an upper 
colonnade of small columns extending at least 10 meters above the lower 
colonnade.  Most measurements are made within 1 meter of the colonnade-
entablature contact.  An image from this site is shown in Figure 3(a).

Site 2: Banks Lake II,  well-formed 10-12 m thick colonnade about 20m 
above the previous site shows excellent wavy columns.  Rubble from this 
site allowed direct measurement of column widths.  Stria heights, wavy 
column wavelengths, and further column edge widths were measured 
through the digital analysis of photographs, where the scale of the images 
was determined by comparing the average side width to that measured in the 
rubble.  The site is in a distinct flow unit from that of site 1, and likely 
cooled from the base up. The observed colonnade is topped by 5-10 meters 
of highly broken up basalt (possibly entablature) and loess, forming the floor 
of the Columbia Plateau.  Images from this site are shown in Figures 1 and 
8(a).

Site 3: Banks Lake gravel pit (47d 40' 58'' N, 119d 16' 24'' W), roadside 
access on Highway 155.  A long stretch of columns shows several large, 
blocky colonnades, sequentially exposed as the roadlevel drops.  Stria 
heights and column widths were measured in the mid-section of a lower 
colonnade at road level, with between a 2 and 5 m thick exposure along the 
highway. Measurements were made on 9 non-adjacent columns over a 30 m 
stretch of highway, as most columns were eroded or broken up. Stria 
curvature and plumose structure indicate the colonnade cooled from the base 
up.  The observed colonnade was topped by a colonnade of smaller columns, 
approximately 10 meters thick, which is presumably an upper colonnade of 
the same flow unit (but with no striae visible).

Site 4: Dry Falls, (47d 35' 16'' N, 119d 20' 35'' W), at the end of the access 
road to Deep Lake.  An exposed hill beneath Dry Falls shows an exposure of 
approximately 20 well-formed columns, 50-100 cm in diameter.  Side 
lengths and joint angles were measured on two nearby sets of adjacent 
columns (numbered 1-14 and 15-22).  The observed colonnade is 5-7 meters 
high, and striae/plumose are eroded.  As there are no additional structures 
exposed at this site, there are no indications as to the cooling direction of this 
colonnade.  A similar, adjacent hill, very likely part of the same formation, 
shows evidence of wavy columns, and is topped by a thin exposure of very 
broken up, blocky colonnade.

Site 5: Park Lake, (47d 34' 57'' N, 119d 24' 48'' W), accessed by a short 
hiking trail leading into a peninsula on Park Lake, 2 km south of Sun Lakes 
campground.  Similarly to the Dry Falls site, several small hills of columnar 
basalt are exposed, due to the action of the Bretz floods.  A 6 m high lower 
colonnade, with large, blocky columns, was studied, with stria heights and 
column widths measured on the upper half of the colonnade over a set of 10 
adjacent columns.  Stria positions were determined with respect to the base 
of the flow. No plumose were seen, but the upward direction of cooling was 
implied by the curving of adjacent striae.  The base of the flow unit is 
slightly vesicular, and the studied colonnade is topped by a short, 1 m thick, 
entablature, and an highly eroded/broken upper colonnade that extended at 
least 5 meters above the entablature.  

Site 6: Lenore Lake, (47d 31' 54'' N, 119d 29' 42'' W), exposed on a cliffside 
west of Highway 17, just north of where it passes over Lenore Lake, 
adjacent to a hiking trail leading west from a small parking lot.  Along the 
cliff, which is not more than 20 m tall, a thick lower colonnade is overlaid 
by a layer of entablature, and a smaller colonnade.  In the cliff's vicinity are 
a number of hillocks composed of curving columns, forming fans, which 
appear to be a continuous with the topmost colonnade on the cliffface.  On 
the fan which composes this field site, the columns are broken off at a point 
where they are nearly vertical.  A patch of approximately 20 adjacent 
columns was selected from this cross-sectional display, on which column 
edges and joint angles were measured.

Site 7: Tucannon River, (46d 30' 30'' N, 118d 0' 15'' W), 10 km southwest of 
the town of Starbuck, on Highway 261.  About 100 meters of well-formed 
lower colonnade, 4-5 m high, have been exposed from blasting during 
highway construction.  The top of the colonnade is not present, and no other 
structures are clearly visible.  The base of the flow is near roadlevel, and 
abuts a vesicular layer of lava below. The columns appear to taper somewhat 
in the top meter of the colonnade, perhaps indicating a contact with a 
missing entablature/upper colonnade near that point.  Striae range 
dramatically in size, from several cm near the flow margin, to a few tens of 
cm away from the flow margin.  Striae curvature and plumose both indicate 
the flow cooled from the base up.  Stria heights were measured, relative to 
their position above the exposed flow base, on a subset of 11 columns from a 
set of about 30 adjacent columns included in the study site.  Column widths 
were measured across the study site.  An image of large striae  from this site 
is shown in Figure 3(c).

Site 8: Lyon Ferry Railway, (46d 33' 38'' N, 118d 11' 04'' W), near Highway 
261, beside abandoned Union Pacific rail tracks, and 1 km south of a rail 
bridge over the Snake River.  At least 3 exposed flow units are visible, all 
blocky and large, in a 25 m high cliff-face. The top of the studied flow unit 
terminates at its top in a 1-2 m thick disordered layer of vesicular material, 
which probably indicates that the observed colonnade at this site is an upper 
colonnade, with a thick crust.  Some striae are visible, but are not in a good 
enough condition to be used to confirm this interpretation of the direction of 
cooling.  Stria heights and column widths were measured 3-5 m below the 
top of the colonnade, on a series of non-adjacent columns spread out over 
approximately 100 m.

Site 9: Little Goose Dam, (46d 31' 55'' N, 118d 8' 42'' W),  on Highway 261 
near Little Goose Dam Road turnoff, a 20-30 m high cliff-face rises beside 
the highway.  At least three flow units are visible in this cliff, the lowest of 
which, accessible at roadlevel, contains a large, blocky, colonnade.  Striae 
curvature evidence implies that this is an upper colonnade, cooling from the 
top down.  The lower colonnade of this flow unit is not exposed.  
Measurements of stria heights and column widths were made 4-6 m below 
what appears to be the upper surface of the flow unit, over a set of 8 adjacent 
columns.  Further interpretation of the flow structures is difficult, due to 
extensive blasting damage.  

Site 10: Chief Timothy I, (46d 24' 44'' N, 117d 11' 25'' W), to the south of 
Chief Timothy campground, adjacent to Highway 12, in the abandoned 
Silcott quarry.  A well-formed lower colonnade dominates the cliff wall, 
with 10-12 meters of height exposed over a cliffface at least 100 m wide. 
The direction of cooling was established by both plumose structure, and the 
curving of striae.  The base of the flow is not exposed.  Wavy columns are 
visible, in places, at this site. Near the west side of the exposure, a recent 
rockfall has exposed a fresh colonnade, light grey in color (much lighter than 
the rest of the dark-coloured cliff), and formed a 3-5 m high rubble pile.  
Measurements of stria heights, column widths, column joint angles, and 
wavy column characteristics were made on an 11 column-wide portion of 
this fresh exposure, from the top of the rubble pile (implying that they were 
taken at least several meters above the lower flow margin).   Additional 
measurements of joint angles and column widths were made on several 
columns of the rubble pile.  The observed flow is topped by an upper 
colonnade, at least 10 m thick (with the top eroded forming the floor of the 
plateau), with smaller-scale columns.  This upper colonnade contains several 
fans of columns, which indicates uneven surface cooling effects.  

Site 11: Chief Timothy II, at a clearing 100-200 m East of Chief Timothy 
site.  The same flow unit is visible, although the upper colonnade is much 
reduced in height, and covered by loess and grasses.  8 m of lower 
colonnade are exposed.  The base of the flow is still not visible. Column 
widths and joint angles were measured on 15 adjacent columns, at ground 
level.

Site 12: Clarkston I, (46d 25' 10'' N, 117d 06' 49'' W), on Highway 12, west 
of the town of Clarkston, beside Evans Road turnoff.  An 8-10 m thick lower 
colonnade consisting of large, blocky columns, is exposed overlying a thin, 
friable soil layer. The presence of a non-basaltic substrate indicates that the 
observed colonnade cooled from the base up, as does the direction of the 
curvature of striae at this site. Above the studied colonnade is a thick 
entablature layer, highly eroded, at least 5 m of which still remains at spots.    
Stria heights and column widths were measured, and stria positions recorded 
with respect to the base of the flow unit, over a set of 7 adjacent columns.  

Site 13: Clarkston II, (46d 25' 19'' N, 117d 07' 25'' W), 500 m west of 
Clarkston I site, probably belonging to the same flow unit, with roadside 
access along Highway 12. Only 3-5 m of lower colonnade (with the cooling 
direction determined by the curvature of striae) are exposed, bounded below 
by the roadlevel, and above by a talus slope which extends to a short 
exposure of entablature, or fans of columns, 30-40 m away.  Measurements 
of stria heights and column widths were made over a series of 19 adjacent 
columns.  Most observations were made 1-2 m above the road level; the 
relative position of these observations within the flow cannot be determined.  

Site 14: Snake River Road, (46d 17' 06'' N, 116d 59' 29'' W), 10 km south of 
the town of Asotin, on Snake River Road.  At least three flow units appear to 
be exposed on a cliffside next to the road.  The roadside provides access to 
an upper colonnade, as indicated by plumose structure and stria curvature.  
At the roadside level, columns are 50-100 cm wide, however they taper to 
about half this size as they approach the upper flow margin, 8 m above the 
roadside level.  Near the upper flow margin, the columns are small, 
somewhat irregular in their direction, and are close to being considered 
entablature.  This colonnade is topped by a thin flow unit, 3-5 m thick, 
consisting of a short blocky lower colonnade, and a thicker vesicular layer 
with no clear jointing structure.  A third, thick flow unit lies over this, and 
extends to the top of the cliff.  On the upper colonnade at roadlevel, that 
forms this study site, stria heights and column widths were measured over a 
series of 17 adjacent columns.  Measurements were made at least 4 meters 
below the upper flow margin. 

Site 15: Asotin Creek (46d 19' 52'' N, 117d 05' 26'' W), 6 km west of Asotin 
along Asotin Creek Road, near a barn.  A long colonnade is visible, with 
large, well-formed columns.  5-7 m of the thickness of this colonnade are 
exposed, although there is no clear indication as to the direction of cooling 
of the colonnade.  The base of the colonnade is below roadlevel, while the 
top of the exposure ends in a short talus slope that extends 5-10 m up to a 
highly eroded, blocky colonnade.  Stria heights and column widths were 
measured over a short stretch of 6 adjacent columns on the roadside 
colonnade. 

Site 16: McCoy Canyon South, (46d 22' 09'' N, 118d 42' 19'' W), accessed 
by walking along the abandoned rail line 2 km south of the end of Snake 
River Road, south of the town of Winddust.  Columns are exposed 
continuously from the road access to the GPS point. A large, but well-
formed, upper colonnade is exposed along the length of the railcut, 
extending about 6 m above the railway at most places. The base of this 
colonnade is not visible.  Columns have faces approximately 1 m across near 
the base of the exposure, but taper to approximately half this diameter in the 
upper reaches of the colonnade.  The studied colonnade is topped by a thin 
entablature, or poorly jointed layer, no more than 1 m thick.  This upper 
layer could be part of the crust of the studied flow unit, or could be a small, 
but separate flow, and was not observed in detail.  Most columns at the study 
site have been damaged by blasting, and reliable measurements of the 
column face width were not obtained here.  Stria heights were measured 
over  5 non-adjacent columns.  

Site 17: McCoy Canyon North, (46d 24' 06'' N, 118d 40' 01'' W), same flow 
unit, and flow structure as McCoy Canyon South site, accessed by walking 
north from the end of Snake River Road, along the abandoned rail tracks.  
The top of the flow unit is more accessible here than at the previous site, and 
stria heights and striae position below the upper flow margin were measured 
over a set of 7 adjacent columns.  Column widths were also measured on this 
colonnade, 1-2 meters below the upper flow boundary.

Site 18: Devil's Canyon Pyramid, (46d 35' 38'' N, 118d 32' 53'' W), 4 km 
north of Lower Monumental Dam, on the east side of Highway 263.  The 
pyramid is a large hill , with a shallow cliff facing the highway, consisting of 
a complex arrangement of interconnecting fans, small vertical colonnades, 
and regions of entablature.  Near the base of the hill, on the south side, is an 
exposure of extremely well-formed columns, inclined about 20 degrees off 
vertical.  The top of this exposed lower colonnade is broken off at the study 
site, but the same flow unit appears to also be exposed further along the cliff, 
where it is topped by a narrow set of fanning columns, that extend into the 
disordered structures of the hillside.  The studied colonnade extends at least 
a few meters below the study site, and copious rubble from this colonnade 
are also present, adjacent the exposure. Plumose structure implies it cooled 
from the base up. Column widths and stria heights were measured over a set 
of 14 adjacent columns.  Further measurements of column widths and joint 
angles were collected from 10 pieces of columnar rubble from this site.

Site 19: Rock River Road,  (45d 46' 04'' N, 120d 20' 29'' W), accessible 
along the roadside of Rock River Road, off Highway 14, 20 km west of the 
town of Roosevelt.  An exposed, large, blocky lower colonnade, 4-5 m high, 
overlies a coarse sedimentary layer, and is topped by an upper colonnade of 
much smaller columns (30-50 cm across).  The face of the upper colonnade 
is set back from the lower colonnade by several meters, and a scree pile, 
composed of debris from the upper colonnade, has formed at one location on 
the cliff-face.  Column widths and stria heights were measured over a series 
of 7 adjacent columns, to the left of the scree pile, and stria positions were 
noted with respect to the base of the flow unit.

Site 20: Rock Creek, (46d 48' 35'' N, 120d 20' 42'' W), on east side of Rock 
River Road, 5 km north of the previous site.  The site consists of a short 
exposure of small, wavy columns, extending no more than 5 m above the 
road level, to a pasture.  Neither the top, nor the base of the colonnade is 
visible, nor are any other structures of the same flow unit.  No striae are 
visible, as the surface of the exposed columns is somewhat eroded.  Column 
widths and wavy column characteristics were measured over a series of 13 
adjacent columns.  

Site 21: Sheppard's Dell, (45d 32' 48'' N, 122d 11' 55'' W), adjacent to the 
entrance of a trail leading to the waterfall of Sheppard's Dell, off Highway 
84, in Oregon.  A 3-4 m high exposure of a well-formed colonnade is 
visible, although somewhat eroded, and partly covered by moss/lichen. 
Neither top, nor bottom, of the colonnade is clearly visible, nor can the 
direction of cooling be determined.  Column widths, and the characteristics 
of wavy columns were measured at this site, over a series of 9 adjacent 
columns.

Site 22: Dell Road, (45d 32' 48'' N, 122d 11' 55'' W), a well-formed lower 
colonnade is exposed on a small hill near the junction of Dell Road and 
Highway 30, off Highway 84, in Oregon.   The direction of cooling was 
determined by observing the curvature of striae.  Only the top 3 m of the 
lower colonnade are exposed, and they are topped by the smaller columns of 
a 3-5 m exposure of upper colonnade, from the same flow unit.  Column 
widths and stria heights were measured over a series of 9 adjacent columns 
from the lower colonnade, and the positions of stria were noted with respect 
to an arbitrary baseline established at the roadlevel.

Site 23: The Dalles Dam, (45d 38' 53'' N, 121d 0' 31'' W), roadside exposure 
on a cliffside directly south of Highway 84, 15 km east of the city of The 
Dalles, in Oregon.  A long exposure of huge, yet very well-formed columns 
(column faces nearly 2 m across on average) of a lower colonnade runs 
alongside the highway.  The direction of cooling can be determined by both 
plumose structure and stria curvature.  The studied colonnade, 15-20 m of 
the thickness of which are visible, is topped by a much smaller entablature 
layer which extends approximately 5 m up to the top of the cliff.  The base 
of the colonnade is not exposed.  Access is permitted along much of the 
colonnade by a small, gently undulating debris fan, fallen from the upper 
entablature.  Variations in the height of this layer show that the columns 
extend more than a couple meters below the roadlevel.  Stria heights and 
column widths were measured over a series of 15 columns, and stria 
positions were recorded with respect to a baseline established at the 
roadlevel.  

Site 24: Deschutes Park I, (45d 39' 06'' N, 120d 57' 14'' W), roadside access 
on the south side of Highway 84, near Deschutes Park, in Oregon.    A 
cliffside approximately 10 m tall, the site is composed mostly of a large, 
well-formed lower colonnade; the colonnade may be a continuation of The 
Dalles Dam site, 5 km away. The direction of cooling was determined 
through the inspection of plumose structure. The top 2-3 m of the cliff are 
more broken up, and may indicate the base of a corresponding upper 
colonnade.  Stria heights and column widths were measured over a set of 5 
adjacent columns on the east side of a wide, dry canyon.

Site 25: Des Chutes Park II, west 50 m across a dry canyon mouth from the 
previous site.  The same lower colonnade is exposed, with no additional 
structures above or below visible.  Plumose structure indicates that the 
columns cooled from the base up.  Column widths and stria heights were 
measured over a series of 9 adjacent columns.  An image from this site is 
given in Figure 3(d).

Site 26: Bingen I, (45d 42' 16'' N, 121d 26' 26'' W), roadside access on 
Highway 14, to the east of the town of Bingen.  A 5 m tall, well-formed 
colonnade is exposed at road level.  It is likely a lower colonnade:  visible at 
its base is the top of an underlying vesicular lava, while the observed 
colonnade is topped by a short, 1-2 m thick, entablature layer, which extends 
up to the clifftop.  Column widths were measured over a series of 9 adjacent 
columns.  Wavy columns were present at this site, but not measured 
quantitatively.

Site 27: Bingen II, (45d 42' 09'' N, 121d 26' 00'' W), roadside access on 
Highway 14, likely a continuation of the flow in the Bingen site, only 1 km 
away.  Wavy columns are conspicuous at this site.  Only a single colonnade 
is visible here, about 5 m tall in its exposure.  The columns are tilted slightly 
to the east, by 5-10 degrees.  A horizontal fault runs through the exposed 
colonnade, 3 m above the roadlevel, with a few cm displacement.  Column 
widths and wavy column characteristics were measured across a series of 23 
adjacent columns at this site.  An example image from this site is presented 
in Figure 8(b).