The phrase "altered gradually" is correct and usable in written English.
It can be used when describing a process of change that occurs slowly over time.
Example: "The landscape was altered gradually as the seasons changed, revealing new colors and textures."
Alternatives: "changed slowly" or "modified over time".
Over nearly all that immense time - 4.5bn years - Earth's appearance would have altered very gradually.
In short, volcanic eruptions, earthquakes, and other violent geologic events may indeed have occurred earlier in Earth history but no more frequently nor with greater intensity than today; accordingly, the surface features of the Earth are altered very gradually by a series of small changes rather than by occasional cataclysmic phenomena.
Over nearly all that immense time, Earth's appearance would have altered very gradually.
The loss of MFL alters gradually from the capillary action to dissolution action.
The results indicated that the patterns of F4-NPs peaks were gradually altered and the baseline of the peaks gradually elevated from CSF-1 through CSF-5 when there was no additional holding after acquisition of chromatograms (left panel of Figure 6).
Artists such as Paula Rego and Kara Walker have gradually altered our ways of seeing.
David Meltzer at Southern Methodist University in Dallas puts the differences down to "genetic drift", a random evolutionary process that gradually altered the appearance of Native Americans over thousands of years.
Nanoparticles like nanohydroxyapatite (nano-HA) were encapsulated into these nanofibers and nano-HA content in the electrospun scaffolds gradually altered in a similar gradient manner to structural organization.
For college players and older teenagers, metal bats were gradually altered to play more like wood bats, their "ping" becoming a "thwunk".
