Could vegetation potentially regrow on vitrified ground?

Question

In this world, a planet with very dense vegetation (earth-tropical-forest-like) and silica containing soil was attacked by spaceships which fired very high energy laser beams across the planet's entire surface, effectively vitrifying it.

• this planet's outer crust was only soil not solid rock or water, life developed thanks to underground water pockets (10 to 50 meters deep)
• the first 8 to 15 meters of soil (depending on location) were fused into glass
• all vegetation in this depth range was immediately incinerated
• some of the plants used to reach down to 20 or 30 meters underground, and a lot of very resilient seeds were disseminated at these levels as well as volatile seeds in the atmosphere
• all of those plants need sunlight and oxygen to develop, but seeds can stay in cryptobiotic-like stasis for as long as thousands of years

question: Could vegetation plausibly break the surface and grow again, after 1300 years time?

Answer 1

It's highly likely vitrified surface will start cracking in a very short time due to thermal contraction initially, then thermal cycles and, in the long term, tectonic activity.

Vegetation is likely to spread from there, given characteristics you state (seed resilience and root depth, mainly).

Depending on specifics of soil and irradiation process you can have either large placques with deep canyons (more likely on rocky ground, but possible elsewhere, particularly where vitrification is deeper) or finer fragmentation in (relatively) smaller boulders.

In the former case vitrified soil would be very evident even after millennia, while in the latter I suspect vitrified rubble to be completely colonized in matter of few centuries.

Other things to note:

• this vitrified soil isn't "lava like" because it's composition isn't mainly silicates, but it's much more varied.
• "Vitrification" is likely to be covered by a lighter stratus of lighter material, possibly rocky foam containing high quantities of high nutritive substance coming from ecosphere destruction.
• liquid "glass" is likely to be a very fluid lava-like thing, at least at beginning, unlike "true glass", so it's likely to flow filling valley's leaving mountain tops (almost) bare.

Answer 2

We already have examples of glassy ground on Earth: volcanic eruptions can give as an outcome obsidian ground, which is basically basaltic glass.

Weathering and erosion makes it possible for vegetation to grow back on this soil after a few years, following a well established sequence: first pioneer plants, followed by more diverse flora.

After 1300 years is very likely you will have to dig deep to find traces of the vitrified soil (look at Pompei).

Answer 3

I think you could work it out in three ways:

• The water pockets you described, due to the extreme heat, "bubbled" outside throught the melted glass, alongside the dormant seeds, and created craters around which vegetation can easily grow because of deeper soil emerging alongside water.

• Such a violent event is unlikely to result in a smooth and perfectly integer glass surface: there will be cracks in it, cracks that can be widened by regrowing plants.

• You can suppose that the ashes of the previously existing plants gathered in valleys and lower grounds, creading an highly alkaline soil, allowing only specific flora to install on it.

Answer 4

If you ignore the fact (or at least the highly likely possibility) that heat which is sufficient to vitrify 15 meters of soil -- bummer is that hot -- will destroy all life in a depth 30 meters as well (it might not incinerate everything, but that's not necessary, some 50-60°C over a period of several hours or days are entirely sufficient to kill everything except thermophile bacteria)... then yes.

Even without the assumption that the glass will crack naturally (or will be cracked by the expanding heated water), this is quite possible. Nature is a tough and unforgiving bastard with eternal patience.

You can reword your question into one that can be immediately answered: "Could vegetation plausibly dig through 70 meters of massive rock?". The answer to that is: Yes of course, that's what you can observe in the underground caves below St. Emillion. The city as well as its vineyards is located on top of one huge, huge rock. There exist man-made (well, man-extended) caves below that rock. And sure enough... roots from the above wineyards come through the ceiling. It takes a vine a mere 80-100 years to achieve that, so 1,200 years for something half the distance should be plenty.

Answer 5

The vitrified surface will rapidly crack and start to weather away, in a matter of 100 years of so there will be sand-like material to grow in.

The problem is twofold though.

1. virtually all plants and their seeds will be destroyed. Even if some seeds survives in deep caves, what is the likelyhood that enough of them will sprout in the same location to form viable growth colonies? 1 or 2, or even 50 of a plant is not enough to establish a viable new growth, due to utter lack of genetic diversity. Additionaly, most plants require the correct micro-organisms in their soil to live. Bacteria and fungi to process the soil so the plant can actually use it. We need to repopulate not just singular lifeforms, but functional ecosystems.

2. The environment will be very toxic to life, for a while.
   The initial heat kills all surface life.
   The 8-15 meter deep layer of molten material covers all of the dry surface of the Earth. It will take many years to cool off to safe levels. Several thousands of years, as the only pathway to heat loss is radiation to space (very slow) or absorption into the ground(faster, but sterilizes the ground!). This is not like a volcanic eruption, tht can rapidly lose heat to the cooler environment. In this scenanario there is no cooler environment left to take the heat.
   In addition, that much heat on the surface will create a lot of nitrous oxides, sulphur dioxides, and release a lot of CO2. The surface will become very acidic, and eventually the oceans will too. This will eventually pass as the now-alkaline virtified material breaks down, but now you've wiped out all complex life in the oceans too, even deep oceans, due to acid shock.

I firmly believe that life will return to the surface.
I equally firmly believe that this life will be of the simplest types.
Anaerobic bacteria at first, because they tolerate both the heat and acidity much better.
The deep, rock-eating bacteria will barely notice that anything happened to the surface. But then, they are not exactly sterling examples of complex, active life.
Later some algae, possibly something as complex as lichens.
I would be very surprised if any complex plant, or any multicellular creature of any level manages to recover from that.