Who Wants to be an Astronaut?
There is a slight difference in terminology for similar features found on Earth and the Moon. The descriptions of the photos that follow will use the proper terms for the Moon with the Earth equivalent in parenthesis. You may want to continue using the same terms as those on Earth or introduce new terminology for lunar features. You will find definitions for the highlighted words in the glossary.
Lunar Image 1
Compare to SRP image #4,5,10,11,12,13
Items of interest:
mare basalts (lava field or flow) rilles (lava tubes or channels) mare ridge (pressure ridge) cones (cinder cones) domes (domes)
Although eruption of most mare basalts did not produce volcanic mountains, there are small volcanic domes in a few places. This shows the Marius Hills, a collection of relatively low domes. Rilles (sinuous lava channels) are also visible, one of which cuts across a mare ridge. Note several volcanic cones across the top of the photo. One has an impact crater on the top. Note the reversed shadowing of the crater and the cone it is on. The rilles appear to issue from them and cut a ridge of basalt that flowed from other cones just off the upper right hand corner of the photo. There is a small pancake-shaped dome left of the large crater, just below center. (Lunar Orbiter V-214-M)
Lunar Image 2
Compare to SRP image #5,13
Items of interest:
domes (domes) rille (lava tubes or channels) wrinkle ridge (pressure ridge) graben (rift)
This image shows two mare domes in northwestern Mare Imbrium. They are located on the rim of an old, mare-filled impact crater. Notice the impact crater on top of the left dome and the reversed shadowing of the crater and the dome itself. There is a sinuous rille out the bottom right corner of the left dome and a wrinkle ridge between the two running down and right. When a load of basalt several kilometers thick is emplaced on the Moon's surface, it causes the underlying material to sag under the extra weight. The resulting motion can cause the surface to buckle, producing a series of ridges on the mare surface, called wrinkle ridges or mare ridges. Also notice a small linear feature below and right of the right dome. It may be a graben associated with a load of basalt being emplaced on the crust. (Lunar Orbiter Image V-182-M, from Wilhelms (1987) The Geologic History of the Moon, USGS Prof. Paper 1348.)
Lunar Image 3
Compare to SRP image #1,2,3,4,5,10,11,12,13
Items of interest:
cones (cinder cones) domes (domes) rilles (lava tubes or channels) basalt flow (lava field or flow)
Shown here are the Marius Hills in Oceanus Procellarum. These hills are the largest group of volcanic cones and domes on the Moon. Note the fairly uniform size and appearance of these features. Also note the sinuous rilles which have formed within the region. Note the dark volcanic cones in the upper right hand corner. They appear more steep-sided and a couple have summit craters. You can see the reversed shadowing of the craters. There are more domes and cones scattered throughout the bottom and left side of the photo. The domes resemble pancakes and most of them can be found along a horizontal line about one-third the way up from the bottom of the photo. They are fairly circular and not very tall but reversed shadowing can be found. One of the domes has three collinear craters on it. It appears that basalt flows may have issued from the cones in the upper right. Notice what appears to be the edge of a basalt flow starting from the lower right hand corner moving up and left with a large tongue pointing down from the center of the photo. Several sinuous channels are evident, one in the lower left corner and two just above the center of the photo. Those two seem to issue from a cone, flow toward the left, and cut through a ridge of the basalt flow front. (Lunar Orbiter image IV-157-H2, from Wilhelms (1987) The Geologic History of the Moon, USGS Prof. Paper 1348.)
Lunar Image 4
Compare to SRP image #1,2,7,9
Items of interest:
dark mantling deposit (ash or cinder) wrinkle ridges (pressure ridge) basalt flow fronts (same)
This image shows one example of a large dark mantling deposit. It is located in Sinus Aestum on the central nearside, and is just east of the crater Copernicus. (Part of Copernicus lies on the leftmost edge of the photo.) It is probably similar to an ash or cinder deposit on earth. The vent is not evident. Wrinkle ridges or flow fronts are seen between and along the three dark, ragged-edged areas. (Earth-based telescopic photo from the Consolidated Lunar Atlas).
Lunar Image 5
Compare to SRP image #6
Items of interest:
wrinkle ridge (pressure ridge) mare ridge (pressure ridge)
This image of the southeastern portion of Mare Humorum shows several wrinkle ridges in the upper left corner. These are common in many mare regions, including Mare Imbrium and Mare Serenitatis. Numerous wrinkle ridges are found at the center of the image. A rift or graben, possibly in response to the crustal loading, is along the right edge of photo. Note that many times the ridges and grabens are parallel. (Lunar Orbiter image IV-137H1.)
Lunar Image 6
Compare to SRP image #1,2,3,7,9
Items of interest:
mare basalt (lava field or flow) flow fronts (same) wrinkle ridges (pressure ridge)
This image shows the southern portion of Mare Orientale. The Inner Rook Mountains cross the center of the image and the Outer Rook Mountains cross the bottom of the image. A thin layer of mare basalt covers the central portion of Mare Orientale (top of picture). Flow fronts are evident. Wrinkle ridges and grabens are numerous in the top half of the photo. A curious feature is found bottom right of the photo just above the line of mountains. It obviously has positive relief by comparing the shadowing to craters and it has either an impact crater or summit crater on top. (Lunar Orbiter image IV-195H1.)
Lunar Image 7
Compare to SRP image #1,2,3,6,7,8,9
Items of interest: flow fronts and lobes (same) wrinkle ridges (pressure ridge) graben (rift)
Wrinkle ridges from basalt load emplacement are found in a curved pattern from right to left, just below the center of the photo. Linear grabens in the lower right parallel the ridges. There appears to be several fingers of a lava flow pointing toward the bottom of the photo that may be break-out lobes from the main mare flow in the top of the photo.
Lunar Image 8
Compare to SRP image #1,2,6,7,9,10,11,12,13
Items of interest:
wrinkle ridges (pressure ridge) grabens (rift) slot vent (same) rille (lava tubes or channels) flow front (same)
The two linear features in the upper right corner are wrinkle ridges or the uppermost one may be a flow front. They both have positive relief. Parallel grabens are found on the upper left side of the photo. The light source is from the right. Notice the reversed shadowing of the wrinkle ridges and the grabens. Just up and right of the center of the grabens is a dome with positive relief. Compare the shadowing to that of the meteor craters. Up and left of the largest crater, at the end of the grabens is a slot vent and rille. Just above the slot vent, to the left of the impact crater with the bright ejecta, is a ridge with positive relief, either a flow front from below or a wrinkle ridge.
Slip Slidin' Away
These two lessons make a connection between geology and mathematics. Use the maps and graphs provided to answer the following questions. There are two ways to approach the mathematics. Consult a mathematics teacher in your school if needed. The solutions presented here were determined using the linear regression capabilities on a graphing calculator. Your solutions may differ slightly and keep in mind these will be averages over millions of years. Plate velocities fluctuate throughout time, so these solutions may not reflect current estimates of plate motion.
Snake River Plain Worksheet
1. Examples of graphs for Method 1.
3. Movement of the North American plate in inches per year.
5. Using East SRP only: movement in inches = 684,000 (M1) to 900,000 (M2) (depends on method) movement in miles = 10.8 (M1) to 14.2 (M2)
6. Using East SRP only: movement in inches = 114 (M1) to 150 (M2) (depends on method) movement in feet = 9.5 (M1) to 12.5 (M2)
7. Direction and rate of the North American plate movement.
Hawaiian Island-Emperor Seamount Worksheet
1. Examples of graphs for Method 1.
3. Movement of the Pacific plate in inches per year.
5. Using Hawaiian Is. only: movement in inches = 14,280,000 (M1) to 5,168,000 (M2) (depends on method) movement in miles = 225 (M1) to 81.6 (M2)
6. Using Hawaiian Is. only: movement in inches = 1050 (M1) to 380 (M2) (depends on method) movement in feet = 87.5 (M1) to 31.7 (M2)
7. Direction and rate of the Pacific plate movement
Note: A straight average over the whole chain gives 3.8 per year over 70 million years. In #1, 10.5 is actually a little high and 3.8 is low. The true velocity lies somewhere in between. The true mileage in #5 lies somewhere between 81 and 225 miles. Prediction equations are just that, a prediction, and are not considered to be absolutely accurate. Much depends on the accuracy of the measurement using the scale. The SRP solutions appear to be more consistent than the HIES solutions.
Beyond the Moon...and Back...to Craters of the Moon
Venus, Earth, and Mars Image. All show rift valleys or grabens.
Mars Image 1
A small, circular volcano with a near circular summit crater. Illumination is from the left. Notice the shadowing on the left side of all three negative relief craters, the summit crater and two impact craters, and lack of shadowing on the volcano itself. Each impact crater has a central peak and the ejecta from the large one has filled the summit crater. Notice the graben cutting the lava plains and the flank of the volcano showing that the graben formed last.
Mars Image 2
This is the volcano Biblis Patera with a summit crater showing evidence of multiple collapse events after eruption. The non-symmetry of the volcano might appear to be wind-blown volcanic debris but a wider picture would show that this is a lava flow around the mountain flowing from right to left. Grabens cut both the volcano and the plain so they formed last. The numerous black dots in a line are markers on the film.
Mars Image 3
The volcano Ceraunius Tholus with a summit crater. Notice the two sinuous channels flowing from the crater. The small one to the west ends in a small fan-shaped flow on the plains, therefore the flow is younger than the plains. The north channel has flowed into the oblong impact crater and created a small lava flow. A meteor striking the surface at an angle most likely formed the oblong crater and its elongated central peak. Notice the reversed shadowing of the impact craters, summit crater, and the volcano itself. The two larger craters at the top of the image show ejecta material around their rims. An interesting study of superposition is shown here. The volcano must be older than the surrounding plains since the erosional gullies on the south flank of the volcano do not end in a fan-shape, meaning the flows of the plain on-lap the flank of the volcano and have covered the erosional material. Then the summit crater may have ponded in a lava lake, occasionally spilling over into the lava channels, which flowed onto the plains. The north channel is found flowing north of the oblong crater but a section through the crater is missing. While the north channel was flowing the oblong crater formed, altering the flow of the channel, now filling the depressed crater.
Mars Image 4
This image shows some large lava flows. The large impact crater on the right shows the illumination must be from the right. The finger-like lava flows in the upper right show a shadow on the left and lighting on the right therefore indicating a positive relief. These flows then have a source from the south and flowed north much like a basalt flow on Earth. The plains show some erosional features of flowing liquid (see arrow), possibly water released from the ground from the heat of the lava flows.
Mars Image 5
The arrow in the middle of the photo is showing the elongated Tempe Volcano. The volcano is aligned with linear grabens suggesting the volcanic material may have reached the surface through a structural weakness in the crust. It may be similar to a cinder cone on Earth.
Mars Image 6
This mosaic shows a series of sinuous lava flows in the Elysium region of Mars. The lava, probably basalt, flowed from south to north (toward the top of the image). (Mosaic of Viking Orbiter images 651A08-651A12)
Venus Image 1
This image shows a chaotic mixture of volcanic features and fractures in the Alta Region. Flower-shaped patterns are created from lava flows emanating from circular pits or linear fissures. Look just above the gray flow in the center for an oblong shaped collapse depression with a 25-mile long lava channel draining it to the north. In the upper rightmost corner are several cones. Several volcanos are found below those, several with sinuous channels. A complex array of fractures and grabens running north and northeast cross the volcanic deposits. Several different flows are radar dark and radar bright.
Venus Image 2
A radar-bright volcano with summit crater is evident just below and left of center. It is a local topographic high, slowing down the northeast trending winds enough to cause deposition of the comet-like material in the eddy behind the volcano. The radar-dark (smooth) areas surrounding the volcano appear to be lava flows with some radar-bright (rough) flow fronts, evident especially above and below and right of the volcano.
Venus Image 3
Seven circular domes dominate the photo. They may be similar to domes on Earth, formed when very thick lava flowed from an opening on relatively level ground allowing the lava to flow in an even pattern. The fractures on top of the domes are interpreted as swelling from the inside inflating the dome after the outer layer cooled and hardened. The bright edges may indicate rock debris on the slopes of the domes. It appears the domes are set on a smooth basalt flow, especially evident at the bottom of the photo. Notice numerous parallel rifts, some of which cut the domes and others that are covered by the domes, indicating that rift formation predates and postdates the formation of the domes.
Venus Image 4
The dark lava flow in the center possibly overlays older, brighter flows. Some of the flows terminate on the bright, sinuous feature on the right suggesting the flows originated from fissures located along this feature.
Venus Image 5
At least five small volcanic cones with summit craters are located on the flank of the volcano Maat in the Ovda region of Venus. Three separate lava flows are shown by the white area on the right, gray area on the left and lower left, and the smaller black area within the cones. The white flow is likely from Maat. Note the lobate features at the top. The gray flow probably laps up to the white flow and overlays the black flow which probably issued from a vent within the cone field. Look in the area where all three flows converge just right of the three cones in the center. The two grabens postdate the black flow and it appears part of the gray flow has filled in a section of the smaller graben.
Venus Image 6
A large sinuous rille. It appears to follow a graben for a short distance in the upper left part of the photo. Numerous parallel grabens are found throughout the image. There may be a dome or cone in the upper left corner.
Venus Image 7
The image shows many volcanic vents in the Lavinia Region of Venus. Some of the vents have positive relief and some appear to be to be vents on the surface. Sinuous riles, similar to those on the Moon flow from the vents, narrowing the further they flow. Lava channels like this on Earth are not generally very wide or long. Since temperatures are high on Venus the lava remains molten for a longer period of time and the rilles are wider and longer than most of those on Earth. The vents may be up to 2 miles wide and the channels may be a half-mile wide.
Bonus Image 1
This pattern of channels on Mars was not formed by lava, but rather water. They show a resemblance to the dendritic (branch-like) drainage systems on Earth, where water acts at slow rates over long periods of time. As on Earth, the channels merge together to form larger channels. However, these valley networks are less developed than typical terrestrial drainage systems, lacking small-scale streams feeding into the larger valleys. Because of the absence of small-scale streams it is thought that the valleys were carved primarily by groundwater flow rather than by runoff of rain. Although liquid water is currently unstable on the surface on Mars, theoretical studies indicate that flowing groundwater might be able to form valley networks if the water flowed beneath a protective cover of ice. Alternatively, because the valley networks are confined to relatively old regions on Mars, their presence may indicate that Mars once possessed a warmer and wetter climate in its early history. The area shown is about 120 miles across. (From Mars Digital Image Map)
Bonus Image 2
This image shows a sand dune field east of Apollinaris Patera volcano on Mars. The dunes do not shift anymore but have hardened into rock, much like sandstone or siltstone on Earth. The craters are younger than the dunes as no dunes are found inside the craters. Illumination is from the left.
Bonus Image 3
The photo shows a small part of the edge of a small impact crater in the floor of the larger Newton Crater on Mars. Note the scale in the lower left corner. Narrow gullies have been eroded into the wall of the crater by flowing water and debris flows (rock and mud slides). The debris transported with the water has formed lobed and finger-like deposits at the base of the crater wall found along the bottom right of the image.
Bonus Image 4
Another Martian windblown sand dune field dominates this image. Unlike Bonus Image 2, the craters found here are older than the dunes since the dunes have formed within the craters. The dunes are aligned east and west with the illumination from the north.
Bonus Image 5
The two yellow arrows show relative movement along a transform or strike-slip fault on the surface of Venus. This is similar to the San Andreas Fault in California and might represent the movement of plates like that on Earth. The fault has left lateral shear, since if you stand on either side and look across the fault, the other side would appear to move to your left. Notice the two grabens in-between the arrows indicating the actual fault where movement occurs. Also notice the two black areas at the ends of the arrows. They may be a lava field that has been ripped in half by the fault making the fault younger than the lava field. The ends of the flows abutting the fault show bending where the lava was stretched and twisted by the fault. Total movement has been about 75 kilometers (45 miles).
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