The Albuquerque Volcanoes

1. The large lumpy outcrops to the left of the trail here are portions of lava flow lobes that flowed away from the Vulcan complex.

2. The trail curves around the base of Baby Vulcan A, a small spatter cone. If you climb to the top of Baby Vulcan A, you can see the small crater rimmed with welded spatter. The rim slopes toward the crater on the northeast side where it collapsed after the eruption. Large gas bubbles can be seen in the surface of the spatter outcrops where gases were trapped in the hot fluid plops of spatter during the eruption.

3. This is the saddle between Vulcan and Baby Vulcan B. Before ascending the trail up the side of Vulcan, you may examine the outcrops of spatter that make up Vulcan B. This small cone is not as symmetrical as Vulcan A back at stop # 2, and there is not a distinct crater, but there are some unusual outcrops here. If you look at the sides of Vulcan from here you will notice that it is not cinder but hard lava and spatter. Most cinder cones are loose cinder and ash. Vulcan is actually mostly cinder and ash. It is just that the last eruptions were of a more fluid spatter instead of cinder. These coated the original cone with a hard shell of solidified lava and spatter - like hard chocolate on a soft, malt-candy interior.

4. Half way up the side of Vulcan there are deep cracks or ledges in the hard lava and spatter on the right side of the trail. If you follow the edge of the ledge you will notice that it outlines a large pie-shaped chunk of spatter and lava. This pie-shaped chunk appears to have moved down the slope. It may have formed by sliding during the later stages of the eruption. Volcanoes, even small ones like Vulcan, swell and vibrate during an eruption. The vibrations and explosions may have cracked and loosened the hard spatter carapace. May have even slid down slope a few feet.

5. Just as you get to the top, there is an arch of spatter. Sometimes it is described as a "lava tube", but it is not actually a lava tube at all. What happened here was the removal of soft cinders and ash from beneath the hard spatter outcrops that coated the rim. Inside the arch you can see a vertical line separating the crater fill from the flank outcrops (on the northeast side of the "cave"). Farther along the south rim of the crater you will find grooves in the lava surface. These formed while the lava and spatter on the rim were still semi-molten and a hard crust moved down slope gouging the plastic lava underneath.

6. The top is flat because the original crater was filled in with late spatter, cinder, and lava. Just to the east of the center of the crater there are bulbous outcrops of spatter. Some of these appear to have been bulged up. The very summit is formed by outward-sloping outcrops of coarse spatter and bombs. If you look closely at the very top of some of these outcrops you will see small melted, glassy patches. These were formed by lightning strikes and are known as fulgurites.

7. Before descending the trail to the other side, you may walk around to the east side of the summit outcrops. Here there is a large cave in the spatter outcrops. Like the cave or arch on the south rim, this formed when the loose cinders were eroded from beneath the hard spatter carapace, just like the arch on the south slope at stop 5.

8. At this point you are standing on the floor of the crater that formed on the north side of Vulcan late in the history of the eruption. The crater formed between the two cones of Vulcan and Vulcan North. The explosion removed the north slop of Vulcan. If you look back up at Vulcan you can see the edge of the lava flows that originally filled the summit crater of Vulcan. Similarly, the large outcrops to the north are lava flows that originally filled the crater of North Vulcan.

9. If you look at these outcrops up close, you will see what appear to be reddish-brown volcanic bombs. These may have fallen into the lava while it was still molten and sank to the bottom of the lava flow. When the explosion removed some of the lava flow, the bombs were re-exposed trapped inside the lava. Or they could be fragments of the cone that rolled down the sides of the cone and fell into the lava stream. If you climb up to the top of this outcrop and go a few feet north you will see unusual sinuous ridges of hard rock. These are very unusual and may be very near surface dikes that intruded the loose cinder cover. Or they could be an unusual expression of the lava channels that flowed away from the cones.

10. The trail skirts around the east flank of Vulcan here. Large blocks of spatter and cinder lay around the base of the slope where they rolled from the outcrops farther up slope.

11. This cinder pit exposes the type of material that makes up most of the cone interiors. Notice that the pieces of cinder and scoria (or "pyroclasts") are rough and have many gas bubbles ("vesicles"). They are not rounded and "fluid-appearing" like the spatter that makes up the surfaces of the cones. This shows that the style of the eruption changed from the time that these cinder and scoria deposits were erupted and the time that the spatter outcrops coating the cones were erupted.

12. The area of the cinder pit was overlain by a later lava flow from Vulcan. You may see this lava flow on the south rim of the cinder pit where it formed dark gray "basalt" lava outcrops. Up close you can see where the hot lava rested on the cinder deposits and how it baked them. look closely at the blocks of lava excavated here and you will see small "phrenocrysts" of whitish feldspar.