It might be fun to estimate the size of this hypothetical super-Hawaii.

The "Big Island" has a height of about 30,000 ft (9 km) above the nearby ocean floor, making it the highest mountain on Earth by that measure. Mt. Everest is highest above sea level (29,000 ft or 9 km), but it is surrounded by the high Tibetan Plateau.

The Big Island's volume is about 100,000 km^3; by comparison, the total volume of lava that went into the Hawaiian-Emperor seamount chain has been estimated at around 10 times this. Scaling the Big Island to that volume means multiplying its dimensions by 2, yielding an above-seafloor height of 20 km. However, the ocean depth near Hawaii is 16,000 ft (5 km). This yields a height of 15 km above sea level, greater than Mt Everest's sea-level height.

Interestingly, the Martian volcano Olympus Mons has a height of 25 km above the surrounding Tharsis bulge; its total bulk is close to that of the Hawaiian-Emperor chain.

Venus has some big volcanoes, but the highest one, Maat Mons, has a height of only 8 km, about that of the Big Island. For some reason, Venus has not produced any super-Hawaiis the way that Mars has, despite its lack of noticeable plate tectonics.