"is gradually expanded" is a perfectly acceptable and usable phrase in written English.
It is usually used to describe a process or concept that is slowly increasing or becoming more complex. For example, "John's knowledge of the subject matter is gradually expanded as he reads more books on the topic."
More commonly, however, the initial small extruded mass is gradually expanded by new lava being forced up into its interior.
With increasing concentration of Anodamine, the passive range of MS in deionized water is gradually expanded.
To avoid aberrations in the expansion optics, the beam diameter is gradually expanded to ~100 times from the output of the optical fiber.
Similarly, the dome-shaped cap of the line profiles is gradually expanded horizontally and vertically as the initial film thickness is increased, which shows the simultaneous growth of Ag NPs in both directions.
The latter option has the advantage that CHP capacity is gradually expanded and eventually the generation capacity exists of a number of smaller CHP units, which enables smoother power regulation and operation of each CHP under full load conditions, which is beneficial for fuel efficiency and technical reliability.
The expanded stent comes along pre-crimped on the balloon (Ø 4.2 mm in its unexpanded state), and is gradually expanded to its final diameter.
Google is gradually expanding its suite of cloud-based offerings.
Just say that what we're doing is gradually expanding Medicare".
The company is gradually expanding into wines -- mostly French with a smattering from North Africa and South America -- and by last year generated annual revenue of $200 million, roughly half from wine.
The company is gradually expanding the technology to its other products.
Many respondents and key informants indicated that the practice is gradually expanding from the agro-pastoral to the pastoral areas.
