Question

formation of earth, formation of the first crust

tell me if its collide or separate

and what plates were involved

Answer 1

Short answer
- Earth formed by collisions (accretion) of planetesimals and at least one giant collision (the Moon-forming impact).
- The planet’s first solid crust did not form by plates “colliding” or “separating” in the modern tectonic sense — it formed by cooling, differentiation and solidification of a global or regional magma ocean (a “separation” of melt and solids), and by extraction/solidification of magmas.
- There were no modern tectonic plates involved in first-crust formation; plate tectonics probably began later (timing uncertain, commonly placed in the Archean, ~3.2–>4.0 Ga in various hypotheses), and the oldest preserved pieces of crust are fragments (cratons) that only participated in later collisions and accretion.

Brief timeline and key points
1. Accretion and core formation (~4.56–4.45 billion years ago)
- Earth grew by collisions of planetesimals and protoplanets. This is a collisional process.
- A giant impact about 4.5–4.45 Ga likely produced the Moon and strongly heated Earth, producing at least one magma ocean.

2. First crust formation (Hadean, >4.0–4.4 Ga)
- As the molten surface cooled, minerals crystallized and either sank or floated, producing the first solids. That process (solidification and chemical separation/differentiation) produced the earliest crustal rocks.
- On the Moon, anorthosite floatation produced a primary light-colored crust. On Earth, the first crust was probably mafic to ultramafic (basaltic) and was repeatedly recycled by impacts and melting.
- Detrital zircons from Jack Hills (≈4.4 Ga) show that some form of continental-like crust and surface water existed very early, but intact continental crust older than ~4.0 Ga is rarely preserved.

3. Emergence of plate-like behavior and continental crust growth (Archean onward, ~4.0–2.5 Ga)
- Whether full modern-style plate tectonics operated in the Hadean–early Archean is debated. Many models invoke an initial stagnant-lid or episodic regime, followed by progressive development of proto-plates, subduction zones and cratonization.
- By the Archean, small protocontinents and cratons formed and later collided and accreted. These later collisions are what built bigger continents.

Which “plates” were involved?
- For the first crust: none in the modern sense — it formed by cooling and differentiation, not by plate collision or rifting.
- For the earliest preserved continental fragments (cratons) that we still see today, examples include the Acasta Gneiss (~4.03 Ga; Canada), Jack Hills zircons (~4.4 Ga evidence; Australia), the Pilbara (Australia) and Kaapvaal (South Africa) cratons (Archean), Slave (Canada), Superior (Canada), Nain (Greenland/Labrador), etc. Those cratons later participated in collisions and rifting episodes that formed bigger continental masses.

Uncertainty and nuance
- Many details (exact timing of first solid crust, when plate tectonics began, and the nature of early plates) remain areas of active research. So answers above give the consensus view plus the main alternatives.

If you want, I can:
- Sketch a simple timeline with ages and processes.
- Summarize evidence (zircons, isotopes, oldest rocks) that supports early crust.
- Describe leading models for how plate tectonics started.