Chapter 12: Geological Evolution of Théxar
"She is not the largest, not the richest, not the oldest. But she is the only one who gave birth to us. And there is no other like her in the entire galaxy." — From the "Hymn of Théxar," classical work of the Flourishing Era
Related sections: → see [Ch.03, "Planet Théxar"], → see [Ch.04, "Biochemistry"], → see [Ch.11, "Ecology"] Key principle: the geological history of Théxar is a chronicle in 10 stages, from planetesimal accretion to the modern tectonic regime. The planet's age (~6.5 billion cycles) determined its calm and mature geological appearance.
Introduction
Théxar — the third planet of the Khar'Vex system, formed ~6.5 billion cycles ago. Its geological history is a chronicle in ten stages, from planetesimal accretion to the modern tectonic regime. The planet has a fully differentiated core, an active mantle, and plate tectonics — these very processes became the foundation upon which life later arose.
From a planetological perspective, Théxar has a number of key differences from typical rocky planets: longer days, an older and calmer geological regime, a different atmospheric composition, and two small satellites instead of one large one. These features shaped the unique evolutionary trajectory of local life.
Geological evolution is not just the history of rocks. It is the history of the atmosphere (tectonics regulate CO₂), the oceans (seafloor relief determines currents), and ultimately — the very possibility of civilization's existence. Convection in the electrically conducting liquid core generates the magnetic field; plate motion is a distinct, thermally connected process. Without volcanism, there would be no mineral-rich soils. Without slow continental drift, there would not be the diversity of ecosystems we observe today.
12.1 Planet Formation
KEY FACT
The formation process of Théxar took about 500 million cycles and ended ~6.0 billion cycles ago. The protoplanetary cloud of the Khar'Vex system was characterized by elevated metallicity ([Fe/H] = +0.12), which provided the planet's core with a rich supply of heavy elements.
12.1.1 Accretion and Growth
The formation of Théxar began with the accretion of planetesimals — small solid bodies enriched in iron and nickel. As the protoplanet grew, gravitational compression and radioactive decay of short-lived isotopes (²⁶Al, ⁶⁰Fe) heated the interior to the melting temperature of iron (~875°X). Gravitational differentiation began: molten iron rushed toward the center, forming the core, while lighter silicate rocks rose to the surface.
Over the following 70 million cycles, the planet experienced intense bombardment — remnants of the protoplanetary disk impacted the surface, increasing mass and releasing thermal energy. By the end of this period, Théxar had reached ~95% of its current mass.
TABLE 12.1: Stages of Théxar Formation
Stage Time (billion cycles ago) Event Duration 1 6.50 ± 0.02 Accretion of planetesimals, formation of proto-Théxar ~20 million cycles 2 6.48 ± 0.01 Core differentiation: Fe-Ni sinks to center ~10 million cycles 3 6.47–6.40 Period of intense bombardment, mass growth ~70 million cycles 4 6.40–6.30 Formation of primary crust, surface cooling ~100 million cycles 5 6.30–6.00 Outgassing of volatiles, primary atmosphere and oceans ~300 million cycles 6 6.00–5.50 First tectonic cycle, emergence of protocontinents ~500 million cycles 7 5.50 Formation of the largest impact basin (Gharra Sea) ~1 million cycles 8 5.50–4.00 Crust stabilization, transition to modern tectonism ~1.5 billion cycles 9 4.00–3.80 Oxygen catastrophe (beginning of photosynthesis) ~200 million cycles 10 3.80–present Modern tectonic regime ~3.8 billion cycles
12.1.2 Impact Event — Gharra Sea
Stage 7 is particularly significant — the impact of a large body (~102–163 мо in diameter) that formed the Gharra Sea basin. This collision was likely so powerful that it:
- Caused partial melting of the mantle in the impact zone
- Created crustal asymmetry — crustal thinning in the Southern Hemisphere
- Influenced the subsequent distribution of continents
- Modified an already active tectonic regime
IMPACT BASIN: Gharra Sea
Parameter Value Basin diameter ~711 мо Age 5.5 billion cycles Consequences Crustal asymmetry, three continents
12.1.3 Origin of Water
Water on Théxar has a mixed origin:
- ~60% — mantle degassing (volcanic emissions of water vapor)
- ~30% — delivered by icy planetesimals from the outer system
- ~10% — cometary material
The elevated metallicity of the protoplanetary cloud provided a greater amount of radioactive elements in the crust, which slowed the planet's cooling and prolonged the period of volcanic degassing. As a result — Théxar received a significant volume of "internal" water, compensating for its somewhat smaller size.
12.2 Internal Structure
PROFILE: Internal Structure of Théxar
Layer Depth (мо) Temperature (°X) State Composition Crust 0–7.1 48.9–386.0 Solid Basalts, granites, sedimentary rocks Upper mantle 7.1–50.8 386.0–766.7 Solid (plastic) Peridotite, olivine, pyroxene Asthenosphere 50.8–91.5 766.7–929.8 Partially molten (~2%) Peridotite + melt Lower mantle 91.5–589.4 929.8–1963 Solid (high pressure) Perovskite, ferropericlase Outer core 589.4–1036.6 1963–2724 Liquid Fe (85%), Ni (10%), S (5%) Inner core 1036.6–1242.3 2724–2942 Solid Fe (90%), Ni (8%), Si (2%)
12.2.1 Crust
The crustal thickness of Théxar varies from 2.4 мо (under oceans) to 9.1 мо (under continents). Average thickness — 7.1 мо. The crust is divided into two types:
- Oceanic crust (~2.4–3.7 мо): basaltic composition, density ~2.8 кх/dL³. Formed at rift zones, recycled in subduction zones. Average age — 180 million cycles.
- Continental crust (~6.1–9.1 мо): granite-metamorphic composition, density ~2.6 кх/dL³. Older — continental cores date to 5.5–5.0 billion cycles.
KEY FACT
Théxar's continental crust contains an anomalously high concentration of thorium (Th) — ~2.5× above standard. This is a result of the elevated metallicity of the protoplanetary cloud. This fact has colossal significance for the energy sector of Xha'Ruun civilization. → see [Ch.09, "Energy"]
12.2.2 Mantle
Théxar’s mantle is the silicate shell between crust and core. Convection carries heat outward and is coupled to lithospheric motion. Melting occurs in particular regions rather than throughout the mantle.
- Lower convection speed
- Larger convective cells
- Longer crustal renewal cycle
The upper part of the mantle (asthenosphere) is a zone of partial melting where magma chambers originate. This is where magma feeding Théxar's volcanoes is formed.
12.2.3 Core
Théxar's core makes up ~32% of the planet's mass. It is divided into a liquid outer core (Fe-Ni-S) and a solid inner core (Fe-Ni-Si). Convection in the liquid outer core generates the planet's magnetic field.
PROFILE: Théxar Core
Parameter Théxar Mass fraction 32% Center temperature ~2,942°X Field strength 42 μT Convection speed ~1.6 мо/cycle
Théxar's magnetic field (42 μT) provides effective protection against the Khar'Vex stellar wind — especially considering the lower activity of the orange dwarf.
12.3 Plate Tectonics
Théxar has active plate tectonics — the movement of lithospheric plates across the asthenosphere's surface. This process is a key factor in the carbon cycle and long-term climate stability.
12.3.1 Plate List
TABLE 12.2: Lithospheric Plates of Théxar
Plate Type Movement speed (па/cycle) Boundary character Kharak Continental 2.4 North — divergent Rhuval Continental 2.1 East — subduction Vexar Continental 1.7 West — collision Thalas Oceanic 3.7 Mid-ocean ridge Gharra Oceanic 3.3 Spreading Koss Oceanic 1.4 Transform Irkhen Mixed 2.2 Subduction Serrin Continental 0.9 Stable Thel Oceanic 0.6 Ancient Polar Ice-oceanic 1.2 Divergent
12.3.2 Continental Drift
Théxar's three continents have not always been in their current positions. Reconstruction of their movement shows:
Geological history of continents
- 5.0 billion cycles ago
Kharak — upper left; Vexar — farther right and lower; Rh — lower right.
- 3.0 billion cycles ago
Rhuval — above; Vexar — lower left; Rh — below.
- Present day
Kharak — above; Rhuval — lower right; Vexar — lower left.
Relative displacement is rightward.
Fig. 12.3. Continental drift of Théxar: from a single supercontinent to the modern configuration.
Drift history:
- 5.0–4.0 billion cycles ago — single supercontinent (Vaal-Kharak) in the equatorial zone
- 4.0–2.5 billion cycles ago — breakup into two landmasses: northern (Kharak) and southern (Rhuval-Vexar)
- 2.5–1.0 billion cycles ago — separation of Vexar from Rhuval, formation of the Gharra ocean
- 1.0 billion cycles ago — present — slow divergence of all three continents
IMPORTANT
Continental drift on Théxar occurs at an average speed of 2.0 па/cycle. The reason is the moderate thermal activity of the mantle. No supervolcanic catastrophe has been recorded in the planet's entire history.
12.3.3 Seismic Activity
Théxar is a tectonically active planet. Average annual number of earthquakes:
| Magnitude | Théxar (per cycle) | Note |
|---|---|---|
| < 3.0 | ~500,000 | Not felt |
| 3.0–4.9 | ~8,000 | Perceptible |
| 5.0–5.9 | ~400 | Moderate |
| 6.0–6.9 | ~40 | Strong |
| 7.0–7.9 | ~4 | Major |
| 8.0+ | ~0.1 (1 in 10 cycles) | Catastrophic |
Reason: moderate speed of tectonic movements and even distribution of stresses.
12.4 Geological Chronology
Théxar's geochronological scale is divided into eras corresponding to major tectonic and climatic phases.
12.4.1 Eras of Geological History
TABLE 12.3: Geochronological Scale of Théxar
Era Dates (billion cycles ago) Duration Key Event Chaotic 6.50–6.00 500 million cycles Formation, bombardment, differentiation Archaic 6.00–5.00 1 billion cycles Crust formation, first oceans Prototectonic 5.00–3.50 1.5 billion cycles Active tectonic cycle, supercontinent Rift 3.50–2.00 1.5 billion cycles Supercontinent breakup, atmosphere growth Biogeological 2.00–0.58 1.42 billion cycles Life's influence on geology (O₂, sediments) Modern 0.58–present 580 million cycles Stable tectonic regime
12.4.2 Oxygen Catastrophe
KEY FACT
Oxygen-producing photosynthesis gradually changed the oceans and atmosphere. Oxygen first reacted with reduced minerals and dissolved substances; it accumulated in the air after those sinks could no longer consume all production.
Consequences of the oxygen catastrophe:
- Mass extinction of anaerobic life forms
- Oxidation of dissolved iron in the oceans — formation of banded iron formations (BIF)
- Formation of the ozone layer — protection from UV radiation
- Change in atmospheric chemical composition: O₂ from trace amounts to ~12%
12.4.3 Glaciations
Théxar experienced at least three major glaciations, each of which left characteristic geological traces:
| Glaciation | Time (billion cycles ago) | Duration | Max. Cover |
|---|---|---|---|
| First (Great) | 3.2–3.0 | 200 million cycles | 45% of surface |
| Second (Kharak) | 2.1–1.9 | 200 million cycles | 38% of surface |
| Third (Rhuval) | 0.8–0.6 | 200 million cycles | 32% of surface |
Interestingly, all three glaciations coincide with periods of minimum tectonic activity — when CO₂ influx from the mantle decreased and the greenhouse effect weakened. The modern polar caps are remnants of the third glaciation.
12.5 Mineral Resources
KEY FACT
The elevated metallicity of the protoplanetary cloud ([Fe/H] = +0.12) and the longer geological history (6.5 billion cycles) led to the formation of Théxar's extraordinarily rich mineral base.
12.5.1 Resource Distribution
TABLE 12.4: Main Mineral Resources of Théxar
Resource Main Deposits Application Iron (Fe) Kharak (Khar-Tor range), Rhuval (Raal plateau) Industry, construction Copper (Cu) Rhuval (Irkhen chain), Kharak (southern coast) Electrical engineering Thorium (Th) Kharak (Thar basin), Rhuval (western spurs) Fission-based nuclear power Uranium (U) Vexar (northern massif) Fuel, medicine Platinum (Pt) Khar'Vex asteroid belt Catalysts, electronics REE Kharak (alkaline massifs) High technology Phosphorus (P) Marine sediments (Thalas) Fertilizers Potassium (K) Evaporites (ancient basins) Fertilizers
12.5.2 Metallogenic Provinces
- Kharak-Tor belt (Kharak): Fe, Cu, Th, Mo — associated with ancient granite intrusions and greenstone belts of the Archaic era.
- Raal Plateau (Rhuval): Fe, Mn, Cr, Pt — layered mafic intrusions of the Prototectonic era.
- Irkhen Chain (Rhuval): Cu, Au, Ag, Zn — volcanogenic massive sulfide deposits of the Rift era.
- Thalas Shelf: P, K, oil, gas — sedimentary basins of the Biogeological era.
12.5.3 Energy Resources
| Resource | Potential | Development Status |
|---|---|---|
| Thorium | Practically unlimited (for thousands of cycles) | Actively used (thorium fission cycle) |
| He-3 | Surface of satellite Thel | Being mined |
| Uranium | Moderate | Auxiliary source |
| Geothermal | High (tectonically active zones) | Regional use |
| Hydroenergy | Moderate | Fully developed |
| Orbital solar | High | Partially developed |
Chapter Summary
Key conclusions:
- Théxar's age (~6.5 billion cycles) led to a calm tectonic regime and mature geological structure.
- Elevated metallicity of the protoplanetary cloud provided unique mineral wealth — with an enrichment factor of 2.5 for thorium and 2.8 for iron.
- Plate tectonics is active, but plate movement speed is low (average 2.0 па/cycle), reducing the frequency of catastrophic earthquakes.
- The oxygen catastrophe occurred 4.0–3.8 billion cycles ago and was gradual.
- Three glaciations in the planet's history are linked to periods of reduced tectonic activity.
- The magnetic field (42 μT) provides effective protection against the Khar'Vex stellar wind.
- Théxar age: ~6.5 billion cycles
- Crustal thickness: 2.4–9.1 мо
- Core temperature: ~2,942°X
- Magnetic field: 42 μT
- Tectonic plates: 10
- Average drift speed: 2.0 па/cycle
- Thorium reserves: 10.9 million ру (enrichment factor 2.5)
- Largest impact basin: Gharra Sea (5.5 billion cycles)
Connections to other chapters:
- → see [Ch.03, "Planet Théxar"] — general planet profile
- → see [Ch.04, "Biochemistry"] — how geology determined the chemistry of life
- → see [Ch.09, "Energy"] — thorium and He-3 as the foundation of civilization
- → see [Ch.11, "Ecology"] — geological factors of biodiversity
- → see [APP:physical-ref] — physical parameters of the planet