Consider the following statements : I. Most magmas are a combination of liquid, solid and gas. II. Water vapour and carbon dioxide are the principal gases dissolved in a magma. III. Basaltic magma is hotter than the silicic magma. IV. The magma solidified between sedimentary rocks in a horizontal position is known as dike. Which of these statements are correct ?

Statements I–III are correct and IV is incorrect. Magma consists of melt (liquid) with suspended crystals (solid) and dissolved volatiles (gas), so most magmas are a three-phase mixture. The principal dissolved volatiles are water vapour and carbon dioxide (with lesser S, Cl, F species) as noted in petrology summaries [1]. Basaltic (mafic) magmas erupt at higher temperatures than silicic (felsic) magmas, making basaltic magmas hotter and generally less viscous [1]. Statement IV is false because a horizontal intrusion along bedding planes is a sill, whereas a vertical, wall-like intrusion is termed a dyke (dike) [2].

Sources

1. [1] https://opengeology.org/petrology/03-magma/
2. [2] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 3: Volcanism and Earthquakes > Landforms of lgneous Intrusions > p. 27