From Persimmon Gap to Boquillas Canyon, Part 7: As the Shadows Fall | Big Bend National Park, Texas, USA
Taken along the western side of Rio Grande Village Road, about 0.2 road mi (0.4 km) northeast of the big Tornillo Creek Bridge. This vantagepoint is a few tens of meters/yards northeast of the Part 6 photo.
I arrived at this site none too soon. A few minutes later the shadow evident at bottom had obscured even the crest of this rise. As it was, though, the low-angle light of late afternoon beautifully highlighted the dike of igneous rock cutting through Upper Cretaceous Pen Formation shale and claystone. The Pen beds closest to the dike were cooked into somewhat harder form when the magma forced its way into them. This is a very localized version of what geologists call contact metamorphism.
Also getting its last dose of direct sun is a scraggily cluster of what I suppose is Faxon Yucca (Yucca faxoniana). This species is better known in Trans-Pecos Texas as Dagger—a fitting tribute to its lethally pointed, rigid, and sword-shaped leaves.
As you can see for yourself on Google Earth, in both aerial and street views, the dike actually runs straight as an arrow on both sides of the road. But, as noted in the previous description, I can find no source that identifies its exact petrologic composition.
To see the other photos and descriptions in this set and my other Big Bend series, visit my my From Persimmon Gap to Boquillas Canyon album.
From Persimmon Gap to Boquillas Canyon, Part 7: As the Shadows Fall | Big Bend National Park, Texas, USA
Taken along the western side of Rio Grande Village Road, about 0.2 road mi (0.4 km) northeast of the big Tornillo Creek Bridge. This vantagepoint is a few tens of meters/yards northeast of the Part 6 photo.
I arrived at this site none too soon. A few minutes later the shadow evident at bottom had obscured even the crest of this rise. As it was, though, the low-angle light of late afternoon beautifully highlighted the dike of igneous rock cutting through Upper Cretaceous Pen Formation shale and claystone. The Pen beds closest to the dike were cooked into somewhat harder form when the magma forced its way into them. This is a very localized version of what geologists call contact metamorphism.
Also getting its last dose of direct sun is a scraggily cluster of what I suppose is Faxon Yucca (Yucca faxoniana). This species is better known in Trans-Pecos Texas as Dagger—a fitting tribute to its lethally pointed, rigid, and sword-shaped leaves.
As you can see for yourself on Google Earth, in both aerial and street views, the dike actually runs straight as an arrow on both sides of the road. But, as noted in the previous description, I can find no source that identifies its exact petrologic composition.
To see the other photos and descriptions in this set and my other Big Bend series, visit my my From Persimmon Gap to Boquillas Canyon album.