Earth Domain

Clerics of elemental earth are straightforward and blunt.  Their faith is simple.  They protect, guide, and serve their disciples.  All else is frivolity in the eyes of the stone born.  They are the rocks of the eternal shore upon which foes break themselves.

Earth Domain Spells

-Bonus Proficiency:  Whenever you choose this domain at 1st level, you gain proficiency with Martial Weapons.

-Terran Disciple:  Also starting at 1st level,  you gain the Mold Earth cantrip.  This counts as a Cleric cantrip, and does not count against the number of cantrips that you know.

-Grounded Healing:  At 1st level, you gain the ability to channel healing energy through the ground to your allies.  All spells you cast that restore Hit Points, regenerate body parts, or resolve physical conditions benefit from a 30ft increase in range.  You and your target ally must both be in contact with the ground for this ability to function.

-Channel Divinity, Turn or Command Elementals:  Starting at 2nd level, you can use your Channel Divinity to cause Elementals to flee.  As an action, you present your holy symbol, and each elemental within 30ft of you that can hear you must make a Wisdom saving throw.  On a failed save, elementals other than Earth elementals, are turned for 1 minute or until it takes damage.  If the Elemental is Earth based they are forced to serve you for 1 minute.  On each of your turns you can issue orders to a commanded Earth Elemental as a bonus action.

     A turned elemental must spend it’s turn trying to move as far away from you as it can, and it can not willingly move into a space within 30ft of you.  It also can not take reactiocns.  For it’s action, it can only use the Dash action or try to escape from an effect that prevents it from moving.  If there’s nowhere to move, the creature can use the Dodge action.

     If the elementals true form is concealed by an illusion, shape shifting, or other effect, that form is revealed while it is turned.

-Stone Sarcophagus:  At 6th level, you gain the ability to summon slabs of stone from the ground to protect fallen allies.  Whenever an ally within 60ft falls dying you may, as a reaction, construct a protective stone barrier around them.  This structure lasts for 1 minute, or until you dismiss it as a bonus action.  While encased the target ally cannot be targeted for attack, and has advantage on all death saving throws.  Once you use this  technique  you must complete a long rest to regain the use of this ability.

-Divine Strike:  At 8th level, you gain the ability to infuse your weapon strikes with divine energy.  Once on each of your turns when you hit a creature with a weapon attack, you can cause the attack to deal an extra 1d8 Bludgeoning  damage to the target.  When you reach 14th level, the extra damage increases to 2d8.

-Terran Awareness:  At 17th level, you gain Tremorsense out to a range of 60ft.  You must be in contact with the ground for this ability to work.

Simple Melee Weapons

Martial Melee Weapons

It seems relatively weak from a power level point of view. Elementals are relatively rare, and the divine strike feature uses a very weak damage type.

From a higher level point of view, I'm wondering what ties the subclass together? What role is this subclass supposed to facilitate in the party? I get some healer vibes from the first- and sixth- level abilities, but the 17th-level ability that the subclass works toward doesn't support that role. Nor do the bonus spells include anything that heals.

Support mostly.  Elemental themed spells in 5e are a bit sparing and lacking in variety, so when it comes to making elemental themed subclasses it can be hard to find enough to fill the chart unless you homebrew completely new ones.  That being said, Clerics as a base class already have access to all the healing and support spells you would need.

For divine strike bludgeoning seems about as close a damage type you can get for someone that focuses on stone and soil,  maybe acid but that seems iffy.

As for the last ability, when considering support, Tremorsense would effectively make you an early warning system for your party.

Magical bludgeoning is quite good, so you might go with that. Force has also been associated with earth by some homebrewers, for lack of a better option.

I agree that the turning CD is too situational. You could expand the creature types and require them to be touching the ground?